wm0415 bird of prey conflicts final version 12 june...

WM0415 Annex B Final Report

12 June 2012

Reviews of selected wildlife conflicts

and their management

Annex B:

Approaches to mitigating bird of prey conflicts with

pheasants at release pens, outdoor poultry

and lambs

A report to Defra


12 June 2012


12 June 2012

Approaches to mitigating bird of prey conflicts with pheasants at release pens, outdoor poultry and lambs

Contents Page Executive summary ................................................................................................................................................. 1

1. Introduction ........................................................................................................................................................ 5

2. Aims .................................................................................................................................................................... 7

2.1 Impacts ......................................................................................................................................................... 7

2.2 Management measures ............................................................................................................................... 7

2.3 Advisory leaflet ............................................................................................................................................. 7

3. Methods.............................................................................................................................................................. 8

3.1 Information gathering and collation ............................................................................................................ 8

3.2 Review of damage by birds of prey .............................................................................................................. 8

3.3 Review of management measures ............................................................................................................... 8

3.4 Evaluation of management measures .......................................................................................................... 9

3.5 Comparison of management measures ....................................................................................................... 9

3.6 Structure of the review ................................................................................................................................ 9

3.7 Advisory leaflet ........................................................................................................................................... 10

4. Recent population trends for buzzard, sparrowhawk and raven ..................................................................... 11

5. Lowland game shooting .................................................................................................................................... 12

6. Review of impacts ............................................................................................................................................. 13

6.1 Diet studies ................................................................................................................................................. 13

6.2 Game birds in and around release pens ..................................................................................................... 15

6.2.1 Direct predation .................................................................................................................................. 15

6.2.2 Indirect effects of birds of prey ........................................................................................................... 19

6.3 Outdoor poultry units................................................................................................................................. 23

6.4 Sheep and lambs ........................................................................................................................................ 25

6.4.1 Impacts of ravens ................................................................................................................................ 25

7. Review of management and control measures ................................................................................................ 27

7.1 Measures targeted at birds of prey ............................................................................................................ 27

7.1.1 Visual deterrents ................................................................................................................................. 27

7.1.1.1 Lasers .......................................................................................................................................... 27

7.1.1.2 Human-scarer ............................................................................................................................. 28

7.1.1.3 Scarecrows ................................................................................................................................. 28

7.1.1.4 Corpses ....................................................................................................................................... 29

7.1.1.5 Eyespots ..................................................................................................................................... 30

7.1.1.6 Balloons ...................................................................................................................................... 30


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7.1.1.7 Kites ............................................................................................................................................ 30

7.1.1.8 Radio-controlled aircraft ............................................................................................................ 30

7.1.1.9 Lights .......................................................................................................................................... 31

7.1.1.10 Mirrors/reflectors ..................................................................................................................... 31

7.1.1.11 Tapes ........................................................................................................................................ 31

7.1.1.12 Flags, rags and streamers (fladry) ............................................................................................ 31

7.1.2 Auditory deterrents ............................................................................................................................. 32

7.1.2.1 Gas cannons ............................................................................................................................... 32

7.1.2.2 Pyrotechnics ............................................................................................................................... 32

7.1.2.3 Shoot to scare ............................................................................................................................. 33

7.1.2.4 Bio-acoustics and other acoustics .............................................................................................. 33

7.1.2.5 Radio- and movement-activated electronic guards ................................................................... 34

7.1.3 Diversionary feeding ........................................................................................................................... 34

7.1.4 Bird of prey removal ............................................................................................................................ 36

7.1.4.1 Translocation .............................................................................................................................. 36

7.1.4.2 Lethal control ............................................................................................................................. 38

7.1.4.3 Egg-oiling .................................................................................................................................... 39

7.1.5 Chemical deterrents ............................................................................................................................ 40

7.1.5.1 Taste repellents .......................................................................................................................... 40

7.1.5.2 Primary repellents ...................................................................................................................... 40

7.1.5.3 Secondary repellents .................................................................................................................. 40

7.1.5.4 Behavioural repellents ............................................................................................................... 42

7.1.5.5 Tactile repellents ........................................................................................................................ 42

7.1.5.6 Repellents in the UK ................................................................................................................... 42

7.2 Measures targeted at the habitat or environment .................................................................................... 43

7.2.1 Exclusion.............................................................................................................................................. 43

7.2.1.1 Netting ........................................................................................................................................ 43

7.2.1.2 Suspended lines/tapes ............................................................................................................... 43

7.2.2 Habitat manipulation .......................................................................................................................... 44

7.2.2.1 Natural and artificial cover ......................................................................................................... 44

7.2.2.2 Perch availability ........................................................................................................................ 44

7.2.2.3 Anti-perching devices ................................................................................................................. 45

7.2.2.4 Screening .................................................................................................................................... 45

7.2.2.5 Zoning ......................................................................................................................................... 45

7.2.2.6 Manipulation of natural landscape vegetation .......................................................................... 46

7.3 Measures applied to livestock .................................................................................................................... 46

7.3.1 Design of livestock units ...................................................................................................................... 46

7.3.2 Livestock practices .............................................................................................................................. 46


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7.3.3 Close shepherding ............................................................................................................................... 48

7.3.4 Prompt removal of fallen or unhealthy stock ...................................................................................... 48

7.3.5 Guard animals ..................................................................................................................................... 49

7.4 Compensation and incentive schemes ....................................................................................................... 50

7.4.1 Compensation schemes ....................................................................................................................... 50

7.4.2 Incentive Schemes ............................................................................................................................... 50

8. Measures currently used in the UK .................................................................................................................. 56

8.1 Gamebird release pens .............................................................................................................................. 56

8.1.1 Measures targeted at predators ......................................................................................................... 56

8.1.1.1 Deterrents .................................................................................................................................. 56

8.1.1.2 Field trials of deterrent techniques ............................................................................................ 57

8.1.1.3 Diversionary feeding .................................................................................................................. 58

8.1.1.4 Lethal control ............................................................................................................................. 59

8.1.2 Measures targeted at the habitat or environment ............................................................................. 59

8.1.3 Measures applied to game birds ......................................................................................................... 61

8.1.4 Current practical guidelines for pheasant release pens ...................................................................... 62

8.2 Outdoor poultry units................................................................................................................................. 64

8.3 Lambs ......................................................................................................................................................... 64

9. Comparison of management techniques ........................................................................................................ 67

10. Discussion ....................................................................................................................................................... 69

10.1 Extent and magnitude of impacts ............................................................................................................ 69

10.2 Mitigation measures ................................................................................................................................ 71

10.2.1 Visual and auditory deterrents .......................................................................................................... 72

10.2.2 Diversionary feeding ......................................................................................................................... 73

10.2.3 Bird of prey removal .......................................................................................................................... 74

10.2.3.1 Translocation ............................................................................................................................ 74

10.2.3.2 Lethal control ........................................................................................................................... 75

10.2.4 Conditioned taste aversion ............................................................................................................... 77

10.2.5 Exclusion techniques ......................................................................................................................... 77

10.2.6 Habitat manipulation ........................................................................................................................ 78

10.2.7 Measures applied to livestock ........................................................................................................... 79

10.2.8 Integrated management strategy ..................................................................................................... 81

10.2.9 Economical management strategies ................................................................................................. 81

10.2.10 Compensation and incentive schemes ............................................................................................ 82

10.3 Consensus building ................................................................................................................................... 82

10.4 European perspective (REGHAB Project) ................................................................................................. 83

11. Conclusions and Recommendations ............................................................................................................... 84

11.1 Pheasant release pens .............................................................................................................................. 84


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11.2 Outdoor poultry units............................................................................................................................... 86

11.3 Sheep and lambs ...................................................................................................................................... 87

12. References ...................................................................................................................................................... 89

Appendix I. Raptor management documents reviewed. .................................................................................... 104

Appendix II. Avian control techniques used against raptors .............................................................................. 110

1 WM0415 Annex B Final Report

12 June 2012

Executive summary Introduction 1. In the UK in recent years, there have been reports of increasing conflict between producer

interests and common birds of prey: specifically buzzard and sparrowhawk predation at pheasant release pens and at outdoor poultry units and ravens predating lambs and poultry. It is estimated that around 35 million pheasants are released each year.

2. In the UK since the mid-1990s, buzzards have shown substantial increases in numbers and an eastward range expansion; raven numbers have fluctuated with some large regional increases; sparrowhawk numbers have remained relatively stable.

3. With respect to wildlife conflicts, Defra policy applies a number of principles that should

be applied in the implementation of management. Defra promotes the use of non-lethal methods but recognises there can come a point when damage caused by wildlife becomes unsustainable and lethal methods of control are required. Defra policy is to issue licences to kill in defined circumstances where further principles should be applied.

4. A study was undertaken that: (i) reviewed evidence for the extent and magnitude of

impacts in the stated conflict areas, and (ii) reviewed avian management approaches to mitigate impacts. The latter focussed on methods applied to birds of prey, both overseas and in the UK and included direct contact with raptor workers internationally.

Impacts 5. Gamebirds form, at most, a very small component of typical raptor diet. 6. Based on historical and average values, in the UK losses of pheasant poults in and

around release pens to raptor predation have been low, commonly (90% of shoots) ≤1% of birds released into pens; representing a small percentage of losses relative to all causes of mortality. The impacts of raptors, however, are not distributed evenly across all shoots. A small number do suffer higher losses, estimated at >5% at one in 30 estates and >10% at some estates.

7. A number of factors were associated with the level of predation at pheasant release pens: POULT AGE: predation declined as the age of poults at release increased; TIMING OF

RELEASE: predation was twice as frequent among poults released in June-July than among those released in August-September; SIZE OF RELEASE: predation increased with the size of the release group; POULT DENSITY: density had no effect on avian predation in releases of <500 birds but in larger releases high densities increased predation; VEGETATION: predation was lower in release pens with >20% shrub cover and pens with at least 60% herb or bramble cover; SIZE OF WOOD: predation was higher in woods >50 acres.

8. Estimates for the impact of birds of prey on outdoor poultry units in the UK are not available. In Bresse, France, a study (1999-2000) revealed that 70% of farmers lost poultry to predation (all predators) with losses per flock of 0-34%. The total loss to predators was estimated as 6.3% of chickens. Although avian predators were responsible for more predation events, mammals killed more chickens per attack and accounted for


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the majority killed. Raptors were responsible for 22% of attacks (goshawk 1%, buzzard 0.4%, unknown 20.6%) and 10% of kills (goshawk 0.6%, buzzard 0.4%, unknown 9%). The comparative figures for crow were 9% and 4% and for fox 6% and 19% respectively.

9. Despite anecdotal reports of indirect losses (e.g. smothering, decreased productivity,

increased susceptibility to disease) studies found no empirical evidence for an effect of raptor activity on either poult behaviour or losses. No known similar studies have been undertaken at poultry units.

10. Estimates for the impact of ravens on sheep and lambs in the UK are not available. In Germany (1990s) a detailed study indicated most contacts between ravens and sheep and lambs were benign. Injury was an exception and involved neglected or diseased young animals, dams who’d suffered difficult births, or animals unable to stand. The killing of healthy animals was not observed. General livestock management conditions were considered to play a crucial role in the accumulation of ravens at lambing parks.

Management 11. Measures to deter birds can be categorised as direct or indirect. Direct measures are

deployed against the birds themselves (bird management), whilst indirect measures are deployed against resources that the birds utilise (habitat management and in this case stock management).

12. The review revealed a wide range of measures that have been deployed. However, there

was very little empirical data and the effectiveness of measures was largely anecdotal. The lack of empirical data prevented any formal analysis to compare the effectiveness of different techniques. There were, however, a number of management themes advocated that were recurrent across different countries and circumstances.

13. From the review, techniques were categorised into four non-mutually exclusive groups,

defined by the target against which measures were deployed: (i) birds of prey, (ii) habitat management, (iii) livestock practices and (iv) other predators.

14. Visual and auditory scaring techniques were reported to vary in their efficacy, from

effective to ineffective. All techniques are subject to habituation and hence of short-term benefit. Habituation can be delayed and effectiveness maximised by integrating a number of different techniques and varying their combinations.

15. Diversionary feeding has received support and some promising outcomes from a number

of sources. The application of diversionary feeding, however, has to follow practical guidelines including placement of the food (which will vary depending on the stock to be protected) and supplying the food in sufficient and regular quotas.

16. Although translocation of raptors to mitigate wildlife-conflicts has been considered to be

largely ineffective in the long-term, the issue of buzzard predation at release pens may have the potential to satisfy conditions necessary for consideration as a short-term measure.


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17. Where raptor impacts are significant and ecological techniques are not effective it has been argued that consideration should be given to the removal (non-lethal or lethal) of particular problem individuals. For ravens, licensed control is undertaken.

18. Conditioned taste aversion (CTA) has been successfully induced in avian predators. The

challenge with inducing CTA is delivering the aversive treatment in a realistic manner that allows the predator to associate the aversive reaction with cues inherent in the prey species. There are significant financial and regulatory issues to overcome in developing and deploying an appropriate CTA agent.

19. Total exclusion techniques (i.e. netting) are usually extremely effective in reducing

predation, but bring significant husbandry and cost issues. The efficacy of partial exclusion methods (e.g. lines and tapes) depends on their integrity, but the greater the level of exclusion the more expensive the method. Exclusion techniques have the potential to interfere with husbandry practices, requiring careful application and limiting their potential use.

20. Changes to livestock practices and environment are a recurring theme in the management

of raptor predation: locate birthing events indoors or near to human activity, retain young animals indoors until they reach a size/weight less attractive to predators, provide shelter and cover in paddocks/pastures, pen design, close shepherding, the prompt removal of dead of unhealthy stock and the use of guardian animals.

21. Control of other avian and mammalian predators might potentially reduce visits from birds of prey, which may be attracted by other predators, such as corvids, as potential prey; there would also be a wider benefit in lower overall predation of livestock.

Conclusions and recommendations 22. The average levels of predation by birds of prey (buzzard, sparrowhawk, raven) are

unlikely to have significant impacts on pheasant poults, outdoor poultry or lambs at the national scale. However, for the small number of holdings that experience higher levels of predation pressure, losses may be more significant and there are a number of measures that can be used to minimise damage.

23. For pheasant release pens recommended options are: ensure sufficient vegetative cover of

shrub and herb layers, natural cover can be supplemented with artificial cover, such as brash piles or ‘wigwams’; minimise opportunities for birds of prey to perch and monitor birds; stock older poults, stock poults at recommended densities (700-1000 per ha); use reflective tape and scaring devices (especially visual deterrents); remove right-angled corners to pens and diversionary feeding. Natural and artificial refuges can also be created outside pens at vulnerable sites, such as feed stations and open-habitat crossing points.

24. For outdoor poultry units recommended options are: provide shelter and cover in

paddocks/pastures specifically the planting of trees; deploy reflective tape and visual deterrents at bird of prey approach points.

25. For lambs recommended options are: locate birthing events indoors or near to human activity, provide shelter or wind protection in paddocks/pastures, retain young animals


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indoors until they reach a size/weight less attractive to predators, close shepherding, the prompt removal of dead or unhealthy stock, if diversionary food is used do not provision in the vicinity of the herd, use of appropriate livestock feeding methods/equipment to prevent access by ravens and the use of guardian animals.

26. A significant number of gaps in knowledge were identified in relation to the quantification of impacts and the efficacy of management measures. Not least that there have been national or regional increases in the population of some of the birds of prey since the completion of earlier investigations. Studies in a number of areas would provide data beneficial to the development of policy in these wildlife conflict areas.

27. Field trials of management measures are generally lacking. This lack of data, however, is confused in some quarters as indicating a lack of efficacy. Field experiments are needed to empirically evaluate a number of techniques

28. Also lacking is information on which to evaluate the efficacy of the removal (non-lethal or lethal) of individual raptors. To enable such an assessment data is required on: the occurrence of ‘problem’ individual raptors specialising on pheasant prey, return rates if birds translocated, turn-over rates of replacement birds and their propensity for pheasant prey and the extent of changes in levels of pheasant losses following removal.

29. Quantitative field trials of deterrent techniques and other measures would be beneficial:

scaring techniques, exclusion, habitat management (i.e. pen protection measures), diversionary feeding and bird of prey removal.

30. Quantification of direct and indirect losses of stock to birds of prey relative to losses to all causes would also be beneficial. Such investigations should not rely solely on questionnaire surveys but should include detailed field investigations. These should focus on sites thought to be experiencing high rates of loss, including identification of factors that may make them vulnerable to predation compared to more typical sites.

31. An assessment of the extent to which producers are aware of recommended guidelines to manage impacts by birds of prey and the extent to which they are implemented.

32. Work to resolve the variety of bird of prey-stakeholder conflicts would benefit from the

establishment of project working groups. Each group should encompass representatives from all relevant interest groups, including ornithological scientists, agricultural scientists, appropriate agricultural sector officials/members and government policy officers.


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1. Introduction The relationship between predators and prey has been a topic of scientific debate for many decades. In birds, predation is a major cause of nest failure (O’Connor 1991; Martin 1993) and may be an important factor influencing the composition and conservation of avian communities (Sih et al. 1985; Newton 1993, 1998). The potential role of predators as limiting factors of prey populations has created a number of human-wildlife conflicts. For birds of prey these include game bird hunting, poultry and other livestock, and more recently avian species of conservation concern. Newton (1988, 1993) stated that of the avian species that have been studied those whose breeding numbers appear most likely to be depressed by predators are ground-nesting game birds and waterfowl. This is probably related to the increased vulnerability of these groups of birds to mammalian predators, in addition to avian predators. Cote and Sutherland (1995), however, concluded that ground-nesting species were not more susceptible to nest predation than species nesting off the ground in open or closed nests; although cavity nesters experienced significantly lower predation than species using any other nest type. In considering the relationship between predation by birds of prey and stakeholder interests it is necessary to differentiate between an effect and an impact in order to identify the existence of a real conflict. Reviews of predator removal experiments (Cote & Sutherland 1997; Newton 1998; Nordstrom 2003; Gibbons et al. 2007; Smith et al. 2010) indicate that in the majority of studies removal of predators resulted in an increase in one or more breeding parameters of birds, i.e. nesting success, post-breeding numbers or breeding numbers. However, although removal of predators often increases numbers of prey alive at the end of the breeding season, different reviews drew different conclusions as to whether there is a consistent increase in numbers of breeders in subsequent years. For wild birds, the existence of high levels of predation is not sufficient to demonstrate that predation is imposing a detrimental impact. Predators may be taking similar numbers of birds that may have died from other causes anyway. In addition, many species have evolved to cope with high levels of predation. For populations of wild birds, the effect of predation may be a reduction in post-breeding numbers but without a subsequent reduction in the numbers of breeding birds in the following year then predation cannot be considered to be having a detrimental impact at the population-level. For game birds, however, the picture is different. For game managers, the important aspect is the depletion of pre-harvest population (the shooting season starts on August 12 to October 1st dependent on the game species), as this will determine the economic impact of predation on hunting activity (Manosa 2002). Predation of young game birds placed into release pens during the summer, therefore, is often construed as a detrimental impact on the estate’s shoot. In respect to game birds and poultry, in addition to direct predation there is also the potential for indirect effects of bird of prey activity. Indirect effects may include deaths from ‘smothering’ that can occur when poultry or game mass within an enclosure in response to perceived danger, reduced production (e.g. eggs) or increased susceptibility to disease through increased stress due to predator presence.


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Predator control is accepted as an integral component of management in the production of game birds and wildfowl for shooting interests. In addition, many conservation bodies undertake small-scale control of predators on their nature reserves (Cote & Sutherland 1995). With respect to wildlife management, Defra apply the following principles: (i) the conflict must be sufficiently serious to warrant such action, (ii) the least severe solution should be applied in order to resolve the conflict, (iii) all other less severe methods of resolving the conflict should be shown to be ineffective or impractical and not just difficult to implement, (iv) the action is cost-effective and proportionate to the actual or potential level of conflict, (v) such action would reduce, or prevent from increasing, the scale of the conflict, (vi) welfare, disease control and conservation obligations are met (Defra 2010). Defra promotes the use of non-lethal methods but recognises there can come a point when damage caused by wildlife becomes unsustainable and lethal methods of control are required. Defra policy is to issue licences to kill in defined circumstances where: (i) all other reasonable non-lethal solutions have been tried and/or shown to be ineffective, (ii) there is a genuine problem/need, (iii) there are no satisfactory alternatives, (iv) the licensed action will be effective at resolving the problem and the action is proportionate to the problem (Defra 2011). Measures to deter birds can be categorised as direct or indirect. Direct measures are deployed against the birds themselves (bird management), whilst indirect measures are deployed against resources that the birds utilise (habitat management and in this case game and poultry management). Each of the categories of bird, habitat and livestock management contains numerous specific techniques aimed at preventing or reducing the detrimental impact (here, impacts on game/livestock). In order to evaluate the cost-effectiveness of any mitigation measure, the cost of implementing the measure has to be considered in respect to the magnitude of the reduction in impacts achieved. For some birds of prey-human conflict areas the extent and magnitude of the impacts are not clear, for example the impact of buzzards Buteo buteo on game poult stocks and poultry interests. Existing research suggests fox Vulpes vulpes predation has the biggest impact on game poults (Robertson 1988; Turner and Sage 2003) but there have recently been a number of license applications for lethal control that claim serious damage is being caused by buzzard predation. The current review focussed on common protected predatory bird of prey species for which there is apparent increasing conflict with various stakeholder interests. Specific predator-conflict issues that were addressed were: (i) buzzards and sparrowhawks Accipiter nisus at game bird release/rearing pens and outdoor poultry units, and (ii) ravens Corvus corax and outdoor poultry units and other livestock (principally lambs). The review examined the available evidence for the extent and magnitude of impacts and the effectiveness of approaches to mitigating these impacts. The impact of birds of prey on free-living game birds and techniques for mitigating such impacts is a very extensive field in its own right (e.g. hen harriers Circus cyaneus and red grouse Lagopus lagopus). Therefore, although the review includes some reference to impacts and mitigation measures on wild-living game birds, detailed coverage of truly wild-living game birds was not within the scope of this review, which instead focussed on ‘wild-living’ game birds post-release until the beginning of the shooting season.


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2. Aims The overarching aim was to review and evaluate the effectiveness of non-lethal and lethal approaches (existing and novel) to mitigate conflict between birds of prey and selected stakeholder interests. The scope of the study was focused on conflict between common raptors (buzzard and sparrowhawk) and pheasant poults at release pens and poultry in outdoor units, and between ravens and poultry and sheep and lambs. Specific objectives were: 2.1 Impacts - To review evidence for the extent and magnitude to which buzzards and sparrowhawks

cause serious damage to:

o Pheasant poult stocks in and around release pens o Outdoor poultry units

- To review evidence for the extent and magnitude to which ravens cause serious damage

to: o Outdoor poultry units o Lambs

2.2 Management measures - To review evidence regarding which approaches (non-lethal and lethal) to mitigating the

impact of bird of prey predation are effective at preventing serious damage by: o Buzzards and sparrowhawks to game birds (focusing on pheasant poults) in

release pens, o Buzzards and sparrowhawks to game birds (focusing on pheasant poults) that have

been released or are ‘wild-living’, the latter relating to birds post-release until the beginning of the shooting season,

o Buzzards, sparrowhawks and ravens to poultry in outdoor units,

o Ravens on sheep and lambs. 2.3 Advisory leaflet - Drafting of an advisory leaflet on non-lethal mitigation measures for managing birds of

prey at pheasant release pens, based on the review’s findings.


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3. Methods

3.1 Information gathering and collation Information was obtained by a comprehensive literature search of standard scientific journals using online reference databases, e.g. ISI Web of Knowledge. In addition, Fera also had access to various bioscience and environmental databases such as Zoological Record, Biosis Previews and Cab Abstracts. Fera also holds an existing comprehensive collection of bird management literature from previous research and reviews (e.g. Bishop et al. 2003). Internet search engines were used to locate further, unpublished, information. The information gathered was collated and summarised. In addition, organisations and workers engaged in research, management and policy toward raptors and other birds of prey, in the UK and overseas (principally in the EU), were contacted for their experiences of measures used to alleviate predation issues: Countryside Council for Wales, Game and Wildlife Conservation Trust, Natural England, Scottish Government, Scottish National Heritage, Welsh Government and individuals from a number of European countries - France, Denmark, Germany, Italy, Spain and Sweden. 3.2 Review of damage by birds of prey All relevant references that were identified in searches were reviewed and the following information on damage by birds of prey was, as far as possible extracted: the country, the affected resource, any patterns of loss, habitat surrounding the resource, period over which damage occurred (i.e. seasonal damage), period of day during which damage occurred (i.e. diurnal pattern), numbers of animals lost or economic loss, whether loss was inferred or measured, identity of evaluator of damage (i.e. stakeholders or independent body) and whether estimates of loss involved replicated and controlled measurements or were one-off assessments. 3.3 Review of management measures There is a very extensive body of literature relating to the management and control of avian species. Much of this, however, was not directly relevant to the present study as it relates to species and circumstances unrepresentative of the issue of birds of prey and livestock (e.g. passerines on crops). The review, therefore, focussed on those documents relating to measures used to deter birds of prey and mitigate the impacts of predation, both in the UK and overseas. In addition to published literature, internet search engines were used to locate further, unpublished, information relating to bird of prey interactions with livestock resources and raptor deterrence/mitigation measures. All relevant references that were identified in these searches were then reviewed and the following information extracted, as far as possible: the technique used, the country in which the work was conducted, bird of prey and livestock species involved, the circumstances and setting, the degree of effectiveness and whether this was inferred or measured. For each mitigation technique, reasons or biological principles behind its use were described, along with any factors or practices that might determine its efficacy; examples of effective use were described, along with examples where its use was less successful.


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In addition to bird of prey-specific documents, measures used against other selected avian species in other settings were assessed for their potential suitability for birds of prey on game birds and outdoor poultry units (e.g. management of piscivorous birds at fisheries). 3.4 Evaluation of management measures Ideally, mitigation and management techniques could be evaluated using the principles of meta-analysis, which is the quantitative synthesis, analysis and summary of a collection of studies (Hedges & Olkins 1985). Such an analysis requires controlled, replicated field trials in which the effect of the management measure is either compared between sites with the treatment and similar sites without the treatment (control sites), or compared at the same site during periods with and without the treatment (‘before-and-after’ experiment). In the event, there were far too few empirical studies to make such an analysis feasible. 3.5 Comparison of management measures The various management options were compared in this study using a scheme based on the Risk Management Options Module of the UK Invasive Non-Native Species Risk Management Scheme (Section 10). This module compares selected attributes of different management options, including effectiveness, cost, acceptability, availability and safety by rating and ranking the attributes using a series of five-point scales. For each attribute of a management option, a low score indicates a ‘positive’ rating of that attribute that might facilitate use of the management option, whilst conversely a high score indicates a ‘negative’ rating of the attribute that might mitigate against adoption of that management option. This comparative scoring was undertaken for preliminary illustrative purposes only. Scoring was based on the present author’s interpretation of information extracted from the various sources and expert judgement. A formal and representative comparative scoring of management measures would require a mathematical synthesis of the inputs from all relevant stakeholder groups (conservationists, policy makers and game managers) (e.g. Redpath et al. 2002, 2004) (see section 10.3). 3.6 Structure of the review The main body of the report is arranged in the following sections: - SECTION 4: Brief summary of recent UK population trends for common ‘problem’ bird of

prey species: buzzard, sparrowhawk and raven. - SECTION 5: Description of a typical release pen and the process of introduction of poults. - SECTION 6: Review of information on the extent and magnitude of impacts of target bird

of prey species on selected livestock (game birds at release pens, outdoor poultry units and sheep and lambs) in the UK.

- SECTION 7: Review of international literature on management measures to mitigate the

impacts of bird of prey predation on selected livestock. - SECTION 8: Review of management measures historically and currently deployed to

mitigate the impacts of bird of prey predation on selected livestock in the UK.


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- SECTION 9: Comparison of the various management measures involving the relative scoring of selected attributes.

- SECTION 10: Overview discussion of the extent and magnitude of impacts of bird of prey

on selected livestock in the UK and the appropriateness, practicality and effectiveness of the management measures reviewed in sections 8 and 9.

- SECTION 11: Conclusions and recommendations to help advise the future mitigation of the

impacts of bird of prey on selected livestock, including the identification of knowledge gaps and areas in which further investigation is required.

3.7 Advisory leaflet From the findings of the review, an advisory leaflet was produced on non-lethal approaches for mitigating impacts by birds of prey at pheasant release pens. The advisory note drew on previously published advice and unpublished observations of interactions between birds of prey and release pens and their management.


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4. Recent population trends for buzzard, sparrowhawk and raven Since 1995, the populations of buzzard, sparrowhawk and raven have shown different trends (Figure 4.1, Table 4.1) – as detailed on the British Trust for Ornithology’s website (www.bto.org).

The buzzard has shown substantial increases in population, including an eastward range expansion, and has arguably become the most abundant diurnal raptor in Britain (Clements 2000, 2002). In contrast, the UK sparrowhawk population has stabilised since the mid 1990s. Likewise for England alone, sparrowhawk abundance increased (170%) between 1975 and the early 1990s, remaining relatively stable thereafter (Baillie et al. 2009). For the raven, marked increases in the UK population between 1994 and 2007 (Risely et al. 2008) were followed by declines, so that the UK population has shown no overall increase between 1994-2009 (Risely et al. 2011). However, there have been steep national population increases in Scotland and Wales (Driver 2006). Ravens have also increased along the English–Welsh border and colonised new parts of lowland England, helping to balance the local declines in northern Britain (Cross 2002).

Figure 4.1 Recent UK population trends (1994-2010) for buzzard, sparrowhawk and raven. From the UK Breeding Bird Survey which is run by the British Trust for Ornithology (BTO) on behalf of the BTO, the Joint Nature Conservation Committee (JNCC) (on behalf of the statutory nature conservation agencies: Council for Nature Conservation and the Countryside, the Countryside Council for Wales, Natural England and Scottish Natural Heritage), and the Royal Society for the Protection of Birds (RSPB).


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Table 4.1 Recent trends in populations of buzzard, sparrowhawk and raven between 1995-2009. Data from BTO/JNCC/RSPB (www.bto.org).

Species UK England Scotland Wales

Buzzard +72* +146* +36* +5

Sparrowhawk -8 -7 - -

Raven 0 -35 +65 +29

Figures from Risely et al. (2011); BTO/JNCC/RSPB

*Denotes statistically significant change

5. Lowland game shooting A description of the typical release of pheasant poults into rearing pens is provided in the Report of the UK Raptor Working Group (JNCC 2000). Birds for release can originate from either a shoot’s own stockbirds (eggs collected and hatched), bought in as chicks and reared by the shoot, or bought in as 6-8 week old poults ready for releasing in July or August. Pheasant poults are introduced into the wild via an open-topped release pen designed to acclimatise the birds to their new environment whilst providing protection against mammalian predators, during the maturation period. Typically, a release pen will be situated in woodland, and consist of a 2m wire netting perimeter fence enclosing suitable natural cover, including trees to encourage a roosting habit (also giving protection from ground predators). As the birds mature they fly out of the open-top of the pen but can return to its safety via specially designed pop-holes and grids in the perimeter fence. Before the start of the shooting season (1st October) birds will have been encouraged to leave the pen to forage and roost in the surrounding areas. The Game and Wildlife Conservancy recommends a pheasant release pen density of no more than 1,000 birds per hectare (700 in sensitive woodlands) (GWCT 2006ab). Using large pens minimises mass kills by mammalian predators, feather picking, and the build up of disease and impact on ground flora (Carroll & Robertson 1997). Poults at release age have a cost of at least £2.50 each. Each pheasant shot has a financial value of up to £33 (derived from the average value of let shooting divided by total bag size). Partridges tend to be released in a different system, involving smaller covered release pens in more open country (stubble) favoured by the species (JNCC 2000). The aim is to keep small groups or coveys of partridges together once they have been released. This is achieved through releasing one or two birds at a time, and providing food and water so that they stay in the vicinity near to the remaining birds in the pen. The GWCT estimates that in the present day nearly four-fifths of shoot providers rely on released pheasants, with around 35 million released each year (http://www.gwct.org.uk/research__surveys/species_research/birds/pheasant/default.asp). The total pheasant bag stands at around 15 million birds, although the bag and probably the population of truly wild pheasants has not increased or has even declined over time. The present percentage of wild-bred pheasants in the harvest is difficult to estimate but may be as low as 10%. Releases of pure red-legged partridges are estimated at about six million birds a year.


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6. Review of impacts 6.1 Diet studies The diet of birds of prey has been studied using both indirect and direct methods. Indirect methods include the collection and examination of uneaten prey remains and/or regurgitated pellets. Indirect techniques have inherent potential biases (Mearns 1982, Oro & Tella 1995, Redpath et al. 2001), with for example, the remains of large and pale prey easier to discover than remains of small and dark prey. Direct methods include direct observation and/or video recording of prey deliveries at nests. Although in some studies there have been some limitations in identifying prey, in others video and film images have allowed the identification to class or family level of most items of prey delivered to the nests of goshawk, common buzzard and rough-legged buzzard (Reif and Tornberg 2006; Tornberg and Reif 2007). A review of studies (pre-1995) on the diet of British and Irish predatory birds found that the mean percentage total mass of the diet made up of birds or their eggs was: all avian species – sparrowhawk 98%, buzzard 50% and raven 19%; gamebirds – sparrowhawk 1%, buzzard 5% and raven 4% (Cotgreave 1995). Buzzard Buzzards are generalist predators that can utilise a number of different hunting techniques – perching and scanning, soaring and walking or standing on the ground (Cramp 1980). This range of techniques allows buzzards to adapt their hunting to suit different habitats and take advantage of a wide diversity of prey, principally mammals (mainly voles Microtus agrestis, Clethrionomys glareolus and rabbits Oryctolagus cuniculus) but also birds, reptiles, amphibians, larger insects and earthworms. A recent Europe-wide review (Valkama et al. 2005) reported the mean proportion of prey items by number in the diet of European birds of prey. For the common buzzard, in 13 studies across 7 countries the mean gamebird component of the diet was 3.3% (<0.1% to 15.1%); the majority of studies (69%) reported values of <5.0%. Sparrowhawk Sparrowhawks hunt solitarily and can use a variety of hunting tactics, including for example short-stay-perch-hunting and contour-hugging flight (Newton 1986; Wilson and Weir 1989). Diet and feeding behaviour were detailed during a ten-year study in southern Scotland, centred on the valleys of the Annan and Esk and encompassing three different habitat types – farmland, sheepwalk and forest plantation (Newton & Marquiss 1982). Sparrowhawks fed almost entirely on other birds; the smaller male hawk taking smaller prey-species (5-120g, especially 5-80g) than the larger female (mainly 20-120g, but up to 500g or more). All bird species of appropriate size present in the sparrowhawk’s foraging range were taken during some period of the year. In April-August, the species taken most frequently were chaffinch Fringilla coelebs, song thrush Turdus philomelos, blackbird Turdus merula , robin Erithacus rubecula, starling Sturnus vulgaris and meadow pipit Anthus pratensis, whilst in terms of weight the most important species were woodpigeon, blackbird, song thrush, starling and chaffinch. Throughout this period large numbers of fledglings were taken, with each prey species increasing in the diet for a short period after its young left the nest. Sparrowhawks switched from one prey species to another coincident with the species’ respective fledgling periods. Breeding by sparrowhawks each year coincided almost exactly with the fledgling


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period of song birds. In September-March, the most frequent prey species were redwing Turdus iliacus, blackbird, fieldfare Turdus pilaris, chaffinch and goldcrest Regulus regulus, whilst in terms of weight the most important were woodpigeon, blackbird, fieldfare and redwing. The diet differed in composition between the three main habitats of the study area, reflecting differences in the local bird populations. Many thousands of pheasant were raised and released throughout the study area. Across all habitats pheasants comprised 0.6% (by number) (0.55%-0.84% per habitat type) of all prey items recorded during April-August; none were recorded in September-March. Partridge were relatively uncommon in the study area and formed 0.08% of all items during April-August. Raven Ravens are omnivorous scavengers and predators (Ratcliffe 1997). In all regions of the UK where raven diet has been studied, sheep have formed a staple food (Marquiss et al. 1978; Ratcliffe 1997). Sheep carrion is a major part of raven diet (Marquiss et al. 1978; Ratcliffe 1997) and ravens are known to occasionally kill lambs (Ratcliffe 1997). An 80% increase in the population of breeding ravens in the Snowdonia mountains, Wales between the 1950s and the period 1978-85, was considered to be most likely related to increased food supply in the form of sheep carrion (Dare 1986). In southern Scotland and northern Northumberland, the decline in the raven population (between the 1960s and the period 1974-75) was attributed to afforestation of former sheepwalk (Marquiss et al. 1978). In these regions, sheep carcasses are an important source of food for ravens (Ratcliffe 1962). In 1974-75, the examination of raven pellets (n=697 from 29 different nesting areas) revealed that sheep wool occurred more frequently than any other animal remains, being present in pellets from all nesting areas examined (Marquiss et al. 1978). Around 3% of pellets that contained wool also contained the rubber rings used to castrate lambs and remove tails. The percentage frequency of sheep remains in pellets declined significantly with increasing afforestation in the area around the nest-sites. In mid-Wales, Newton et al. (1982) studied populations of ravens and buzzards in relation to sheep farming and forestry. Breeding densities of both species were the highest recorded in Britain. Examination of raven pellets (n = 789) from nest sites (n = 30) and various roosts and food sources showed that territorial ravens (i.e. remained on their territory all year) depended heavily on sheep carrion – found in 92% of pellets from the breeding season and 86% of pellets from the rest of the year. On average, stocking densities on the sheepwalk were around 150 ewes per km2, and carrion represented by 5 adult sheep and about 45 lamb carcasses per year. Other mammals important in raven diet are lagomorphs (hares and rabbits) and small rodents (voles and mice) which are both killed and scavenged (review of diet in Ratcliffe 1997). Other smaller component items of the diet include birds, invertebrates and vegetable matter.


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6.2 Game birds in and around release pens

6.2.1 Direct predation

There have been a number of empirical studies that have quantified predation losses of pheasants in and around release pens in the UK. The existing studies and reviews are chronologically summarised below and in Tables 6.1 and 6.2. Losses to predation need to be considered in the context of overall losses to all causes. Once released into pens, pheasants can perish before the start of the shooting season from a number of factors: starvation, exposure, disease, predation, natural causes or accidents. In a recent study that monitored the fate of radio-tagged birds, 25% of pheasants died before the start of the shooting season (from all causes). The return rate (i.e. the percentage of released birds that were subsequently shot) was 37.5% (30.5% shot on the estate and 7% shot off the estate) (Turner and Sage 2003). Lloyd (1976a): this study (1973-75) for the British Field Sports Society, Royal Society for the Protection of Birds (RSPB) and the Wildfowlers Association of Great Britain and Ireland (latterly BASC) found that tawny owls Strix aluco, sparrowhawks and buzzards (in that order) were mostly involved in attacks on pheasants at release pens. Not all reported losses, however, could be assigned to these or other raptors; mammalian predators were also involved. The extent of raptor predation was estimated from three sources: (i) a survey of estates (154 estates over three years), (ii) the National Game Marking Scheme (NGMS) (Game Research Association/Game Conservancy), and (iii) case studies. The numbers of poults lost, to raptor predation expressed as a percentage of the total numbers of birds released into pens, was 0.9% (estate survey), 0.3% (NGMS) and 0.2% and 0.1% (case studies). It was considered that the value from estates represented an over-estimate for the country as a whole due to bias in the survey, i.e. the sample was non-random with a bias towards estates that had reported cases of avian predation. The true figure nationally for avian predation was considered to be about 0.25%. Avian predators accounted for about 5% of known deaths to all causes of reared pheasants. Two thirds of shoots visited during the study lost <1% of birds released and one shoot in ten lost >5% of birds. Again, adjusting for the bias in the survey, the true figure nationally was considered to be that 90% of shoots lose <1% of released birds and only one shoot in 30 (3.3%) losses >5%. It was acknowledged that as between a third and a half of estates reported killing birds of prey, if they had not done so losses would have been greater. This was estimated between 2% and 5% of birds released, representing between 0.7% and 1.7% nationally. Lloyd (1976a) reported that a common belief held by gamekeepers was that tawny owls engaged in mass kills, i.e. the killing of a large number of poults in a single night. The study, however, revealed no evidence that mass kills (>10 birds) were attributable to tawny owls (or other avian predator). In 18 of 22 mass kills evidence indicated mammalian predators to be responsible. In only four cases was it not possible to either dismiss or attribute mass kill to a tawny owl. Investigation of factors that affected avian predation revealed:


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- POULT AGE: predation declined as the age of poults at release increased. Most kills

occurred when poults were aged between 6 and 9 weeks. Sparrowhawks were reported killing poults up to 12 weeks old, tawny owls up to 12.5 weeks and buzzards up to 14 weeks.

- TIMING OF RELEASE: predation was twice as frequent among poults released in June-July than among those released in August-September.

- SIZE OF RELEASE: predation increased with the size of the release group. - POULT DENSITY: density had no effect on avian predation in releases of <500 birds but in

larger releases high densities increased predation. - VEGETATION: release pens with >20% cover of shrub layer were predated less than pens

with <20% cover. Pens with at least 60% cover of herbs or brambles were predated half as much as pens with more open herb layers. Pens without either shrub or herb layer were very susceptible to predation, particularly to large losses and mass kills.

- SIZE OF WOOD: releases in woods >50 acres in size were more susceptible to predation than those in smaller woods. Pens extending out of a wood were more liable to large losses and mass kills than those completely within the wood.

- Factors that were found not to significantly affect predation were: WING CLIPPING, SIZE OF

PEN, TYPE OF TREE WITHIN PEN and TREE COVER. Robertson (1988): used re-sightings of individually tagged birds to monitor the survival of 250 six-week-old pheasants placed in an open-top release pen, in Co. Kildare, Ireland in 1983. Clipping of the primary feathers on one wing restricted flying ability for approximately two weeks. Individual birds emerged from the pen between one and 72 days after release into the pen (mean = 27 days). Birds suffered their highest rate of loss (48%) during their first 10 days outside the pen. Sixty-seven percent of known losses (n = 132) were attributable to predation, with foxes responsible for 61%. There were 115 unexplained disappearances. Foxes were initially attracted to the area by the presence of inaccessible prey rather than the density of birds outside the pen (Robertson & Hill 1986). It was suggested that, in unkeepered Irish conditions, a lower density of birds within each pen, or a number of widely dispersed pens may decrease the attractiveness of the area to predators prior to birds emerging from the pen and increase their subsequent survival increase subsequent survival. The study involved a single pen on unkeepered land in Ireland and loss rates were much higher than normally encountered on keepered estates. Other studies of the release of birds onto unkeepered land have also identified the immediate post-release period as the time when most losses occur. In USA, Hessler et al. (1970) recorded losses of 81% in the 28 days following release and that predation accounted for 90% of all known losses. This study involved a ‘hard’ release of pheasants (i.e. immediate release without the use of pens). Also in USA, Burger (1964) noted losses of 65% within the first week after release with 42% due to predation. Harradine et al. (1997): to assist the UK Raptor Working Group’s assessment of whether raptor species were giving cause for concern to game managers (JNCC 2000), the British Association for Shooting and Conservation (BASC), undertook a survey of its gamekeeper membership (Harradine et al. 1997). Information provided by almost 1,000 gamekeepers was subsequently assessed, with 61% of participating gamekeepers (3,900 questionnaires distributed) reported problems caused by raptor predation. Concerns were greatest in


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lowland areas and centred primarily on raptor attacks on pheasant and partridge in and around release pens. The species involved in the majority of reported incidents were sparrowhawk (36%), buzzard (20%) and tawny owl (17%). Incidents involving different game birds were: pheasant 63.9%, partridge 17.6%, grouse 13.2%, duck 1.2%, other 4.1%. Half (51%) of all incidents involved release pens, nearly all of which were pheasants. A marked seasonal pattern in the incidents related to the availability of stocked release pens in the late summer and early autumn (July-September), as well as the availability of growing birds both outside pens and newly released. Quantification of the losses of birds to raptors was possible for some of the estates, with mean losses (expressed as a percentage of the number of birds released into pens) of under 5% and often under 1%. For individual species estimated mean losses were: sparrowhawk 1.9%, buzzard 3.2%, tawny owl 1.8%. At some shoots losses were higher at over 10%. Allan et al. (2000): this study, prompted by the findings of Harradine et al. (1997), aimed to address a number of the gaps in knowledge relating to raptor predation at game bird release pens. The study included 20 estates distributed from Avon to Northumberland. The objectives were: (i) to quantify losses to raptors and other predators, (ii) to evaluate the influence of habitat and management practices, including the use of deterrents, in determining the magnitude of such losses, and (iii) to assess the impact of recorded losses on the game management interests of participating estates. Data from counts and examination of carcasses by keepers was used to estimate losses of poults and to identify the type of predator responsible (mammal or bird) – kills were not identified to species of predator. Estimates of losses to birds of prey, expressed as a percentage of the number of birds released into pens, were calculated using data from 28 pens over 14 estates. Using what the authors considered to be the most realistic of three estimation methods, the median loss was 0.8%. Seventeen pens had ≤1% poults lost to avian predators and only 6 pens had losses of over 2%. The most liberal estimation method (i.e. all carcasses with signs indicative of either bird or mammal were attributed to birds) produced a median loss of 1.1%; 13 pens had losses of ≤1% and only 9 pens had losses over 2%. The release pens varied in size and age. The majority of pens were ≤1ha in area, a further two were 1-2ha and only four pens were >2ha. Poult stocks varied from 100 to 2,500 poults (median = 1,000) with a median density of 1,500 poults per ha. Levels of raptor predation were related to the density of vegetation at a height of 1.5m above ground and to the age of the pen - predation was highest in pens that were older and with lower foliage density. Kenward et al. (2001a): investigated factors affecting predation by buzzards on released pheasants in Dorset, southern England. The study used: (i) observations of 40 buzzard nest sites to obtain estimates for kill-rates, (ii) radio-tracking of 136 buzzards to obtain data on their presence at pheasant-release pens, (iii) the records of 10 gamekeepers to assess levels of predation and (iv) habitat characteristics for any relationship with the presence of buzzards. The study used 28 release pens with flocks of between 30 and 1,000 juvenile pheasants (aged 5-7 weeks) released into each pen during July. In total, in 1994 10,200 birds were released into 27 pens and in 1995 10,525 birds into 28 pens.


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Over two years (1994-1995), gamekeepers estimated that 1,971 (9.5%) of released pheasants were killed by predators: buzzards 4.3%, tawny owls 0.7%, sparrowhawks 0.6%, corvids 0.1%, foxes 3.2% and other mammals 0.6%. There was considerable variation in the estimated number of buzzard kills across the 55 releases (i.e. 27 pens in 1994 and 28 pens in 1995). No pheasants were killed on 9 occasions (16%) and <20 kills in 23 releases (42%). Only 21% of releases had >2 pheasant kills per week. There were some cases, however, where kills were higher: 35-40 pheasants in 12 (22%) releases, including two occasions when losses exceeded 20% of the released birds. Fresh pheasant remains were found in six of the 91 visits to buzzard nests (7%); a different nest on each occasion representing 15% of the 40 nests. The estimated kill-rate was 0.017-0.033 pheasants per day for each member of the pair provisioning each nest during May-July. Examination of prey remains at nests showed that pheasant comprised only 2.6% of the 233 prey items. The dominant prey item was rabbit Oryctolagus cunniculus. Looking at relationships between predation and release-pen variables, buzzards tended not to kill pheasants when there was above-average shrub, below average deciduous canopy and relatively few pheasants present in the pen. The number of pheasant killed was greatest in large pens with extensive ground cover, and the highest proportion of pheasants was killed in large pens where few were released, i.e. at low density. Thirty-six radio-tagged buzzards were recorded at pheasant pens. Buzzards were located most often at pens with open, deciduous canopies. Pens were most likely to be visited by buzzards that had fledged nearby but the proximity of nests had little influence on how much predation occurred. Despite 44% of buzzards having a pheasant pen within their home range, only 8% (11 birds) recorded an appreciable association with a pen. These 11 birds formed two distinct categories: eight buzzards with less than 20% of their locations at pens and three buzzards with at least 50% of their locations at pens. The mean number of radio-locations was 12 (range 5-24) during August-October of their first year within 1km of the study area. The study concluded that buzzards were responsible for a small proportion of total losses. Also, it was considered that the few instances of heavy losses could be avoided by encouraging shrubs rather than ground cover in pens, by siting pens where there are few perches for buzzards, and perhaps by high-density releases. Turner & Sage (2003)/Turner (2007): undertook a Game Conservancy Trust three year study, at six large rearing estates in southern England, which investigated the mortality of released pheasants in relation to density of the release and the quality and management of the local habitat. In each of six open-topped release pens 24-30 birds were fitted with radio-tags (out of between 400 and 2000 birds per pen) and relocated several times a week over the pre-shooting and shooting periods. Of 325 radio-tagged birds, 255 were lost between release in July/August and the start of shooting in late-October/early-November. At the end of shooting 16% of birds still survived. Of the tagged birds 23% were predated or scavenged before shooting began – the great majority by foxes. A further 13% were predated or scavenged


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during the shooting season (some of which may have been shot but not picked up). Of a total 486 radio-tagged birds it was believed that three (0.6%) were killed by raptors. The study found that steady losses of birds occurred between releasing and shooting with the extent of mortality varying greatly between release pens. The average on-estate shooting return from pens was 30% (36% if including off-estate returns). There was no relationship between survival of radio-tagged birds and stocking density. However, the proportion of the released cohort that was shot was significantly reduced as the stocking density of the pen was increased. It was suggested that desired bags could be achieved if all pens were stocked at lower density but with an increased number of pens. Survival to the start of the shooting season increased with delayed release dates. It was suggested that, in terms of survival, an optimum releasing strategy would involve delaying the release of birds until late August-early September, and leaving a minimum period for birds to mature before commencing shooting. Previous reviews: the recent reviews ‘Report of the UK Raptor Working Group’(JNCC 2000), ‘Impacts of Predatory Birds on Waders, Songbirds, Gamebirds and Fisheries Interests’ (Park et al. 2005) and ‘The Impacts of Birds of Prey on Gamebirds in the UK’ (Park et al. 2008) detailed the same studies as described above. One further review on ‘The Predation of Wild Birds in the UK: a Review of its Conservation Impact and Management’ (Gibbons et al. 2007) reviewed the evidence for the impacts of predators on wild-breeding game birds but did not address the issue of predation at release pens.

Reconciling Gamebird Hunting and Biodiversity (REGHAB Project) (2001-02): the EU Concerted Action Reconciling Gamebird Hunting and Biodiversity (REGHAB) project aimed to create the first step to reach long-term, sustainable solutions to reconcile gamebird hunting and biodiversity conservation across Europe.

Amongst a number of conclusions arising from the project (Arroyo 2002; Arroyo and Vinuela 2002a; Arroyo and Vinuela 2002b; Vinuela and Arroyo 2002) was that there was limited scientific information on the effect of predation on populations of gamebirds, and in most cases it was not clear whether mortality caused by raptors was additive or compensatory. As a general rule, it was uncertain that raptors caused substantial losses to hunting bags. When compared to other factors, such as changes in habitat quality, predation by raptors may be a relatively minor factor in limiting gamebird populations. It was also concluded, however, that in certain circumstances, raptors (in these cases hen harriers or goshawks Accipiter gentilis) can cause a significant decrease in the number of birds available for shooting in the autumn or limit gamebird populations, e.g. red grouse in Scotland, grey partridge in France, pheasants in Fennoscandia and tetraonids in boreal forests.

6.2.2 Indirect effects of birds of prey

Lloyd (1976a) reported gamekeepers’ claims that the disturbance caused by birds of prey was more serious than the actual killing of pheasant poults. In respect to buzzards, for example, ‘...as many of the complaints by gamekeepers against buzzards are over the disturbance they cause to game and not the numbers they kill...’. Lloyd (1976) recorded three categories of complaint:


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- Tawny owls attacking poults at roost causing them to fly to the ground where, if they are

outside the pen they are more vulnerable to mammalian predators, mainly foxes. Repeated attacks and even the presence of owls were reported to deter poults from going up to roost.

- The presence of sparrowhawks and buzzards at a pen or feeding site causing birds to desert the area and straying over the shoot boundary or going to parts of the shoot where they are not wanted, for instance areas where it is difficult to present them over the guns well.

- Disturbance by sparrowhawks and buzzards in release pens causing poults to be

frightened to come out of cover to feed, resulting in depressed growth and poor condition. A further complaint is of ‘smothering’ events as a result of poults massing as a result of panic induced by the presence of a bird of prey.

Following observations at release pens Lloyd (1976a) concluded that although the effect of disturbance of reared poults by birds of prey could not be quantified, the importance of any effects was probably over-estimated. Lloyd’s (1976a) observations indicated that the mere presence of owls at or near a pen had no effect on roosting poults; neither did owls calling or playback of the taped calls of owls or young owls’ begging calls. Only the birds in the immediate vicinity of an owl attack left the roost. The disturbance caused by the arrival of a buzzard in the vicinity of a release pen and feed ride was construed by one gamekeeper to be responsible for the loss of 50% of the birds from this wood. Despite no kills during the five-day period that the buzzard was present, the number of pheasants regularly feeding at this site declined from around 100 to 20-30 birds. Numbers subsequently recovered to around 50. However, the incident occurred when the poults were about 12 weeks old and would have begun to disperse irrespective of any putative disturbance. Observation of incidences when a sparrowhawk flew through a release pen revealed minimal effects on the poults. The birds froze momentarily then resumed feeding when the sparrowhawk had disappeared. More recently a survey by the British Association for Shooting and Conservation (BASC) of revealed that gamekeepers perceived birds of prey to impose indirect impacts at release pens (Harradine et al. 1997). Many keepers reported that an attack by a raptor on birds particularly within a release pen but also once outside it had effects on the remaining birds, including reluctance to feed or come to roost, widespread dispersal outside the pen, and similar damaging effects. Consequences of these indirect effects were considered to include further losses to other predators, primarily foxes. A subsequent study on predation at pheasant release pens failed to confirm high indirect losses (Allan et al. 2000). No relationship was found between the frequency with which raptors occurred at release pens and losses to causes other than direct raptor predation. The study postulated, however, that although not substantiated in the analysis, such indirect losses may only become apparent under exceptional predation levels. Also, that some indirect effects may be non-lethal for which the study was not designed to detect.


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Table 6.1. Summary of studies of raptor predation at pheasant release pens – estimates of losses.

REFERENCE STUDY

AREA/YEAR

DATA (N) PREDATOR MEAN

(%)

MIN.

(%)

MAX.

(%)

ECONOMIC POTENTIAL SOURCES OF BIAS/LIMITATIONS

LLOYD 1976Aa

GB

1973-75

ESTATE SURVEY (154/ 3 YEARS)

NGMSb (1964-1973)

CASE STUDIES (2 AREAS)

[TAWNY OWLS

SPARROWHAWKS

BUZZARDS]

0.9c

0.3d

0.1-0.2e

0

0

ND

>10

0.73

ND

ND

NON-RANDOM SAMPLE OF ESTATES

OFTEN INCOMPLETE DATE FROM KEEPERS

WRONG ASSIGNMENT OF KILLS TO PREDATOR TYPE

LOSSES NOT ASSIGNED TO INDIVIDUAL RAPTOR SPECIES

UNDER-RECORDING OF LOSSES TO DISEASE & WEATHER

ROBERTSON 1988 CO. KILDARE

1983 RELEASE PEN (1)

FOX

UNIDENTIFIED

61f

ND

ND

ND

ND

5 ND

ONLY A SINGLE PEN STUDIED

ATYPICAL UNKEEPERED SITUATION

HARRADINE ET AL. 1997 GB

1995 KEEPER QUESTIONNAIRE

SPARROWHAWK

BUZZARD

TAWNY OWL

1.9

3.2

1.8

0.05

0.02

0.07

20.0

46.7

15.0

ND BIAS FROM QUESTIONNAIRE SURVEY


ALLAN ET AL. 2000 GB

1999 ESTATES (14)

BUZZARD

SPARROWHAWK

TAWNY OWL

0.8

[MEDIAN] 0.0 4.7


LOSSES NOT ASSIGNED TO INDIVIDUAL RAPTOR SPECIES

KENWARD ET AL. 2001A DORSET

1995

RELEASE PENS (28)

PREY REMAINS AT NESTS (40)

KEEPER RECORDS

RADIO-TAGGED BUZZARDS (136)

BUZZARD

TAWNY OWL

SPARROWHAWK

CORVIDS

FOX

OTHER MAMMALS

4.3

0.7

0.6

0.1

3.2

0.6

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND LARGE ITEMS IN PREY REMAINS MORE EASILY RECOVERED

BIAS FROM KEEPER SURVEY

TURNER & SAGE 2003/

TURNER 2007

SOUTHERN

ENGLAND

2001-04

RADIO-TAGGED POULTS (486) UNIDENTIFIED RAPTOR

ALL PREDATORS

0.6

23

ND

ND

ND

ND

ND

NO DATA DURING FIRST THREE WEEKS AFTER RELEASE

a Mean losses to raptors (all species) = 0.25%

b NGMS = Game Conservancy’s National Game Marking Scheme.

c Estate survey - values refer to ‘avian predation’ as losses not assigned to individual species of birds of prey.

d NGMS - values refer to ‘avian predation’ as losses not assigned to individual species of birds of prey.

e Case studies - values refer to ‘avian predation’ as losses not assigned to individual species of birds of prey.

f Foxes were attributed responsible for 61% of the total 66% of poults lost.

ND = No data


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Table 6.2. Summary of studies of raptor predation at pheasant release pen - association between habitat variables and levels of predation.

REFERENCE BIRD PREDATORS MAMMAL PREDATORS DATA VARIABLE PREDATION LOWER

LLOYD 1976A

TAWNY OWL

SPARROWHAWK

BUZZARD

UNIDENTIFIED

CORRELATION BETWEEN

RELEASE PEN HABITAT

VARIABLES AND

PREDATION

POULT AGE

TIMING OF RELEASE

SIZE OF RELEASE

STOCKING DENSITY

VEGETATIVE COVER

SIZE OF WOOD PEN SITED IN

WING-CLIPPING

PEN SIZE

TYPE OF TREE WITHIN PEN

TREE COVER

OLDER POULTS

LATER RELEASE (AUG-SEPT < JULY-AUG)

SMALLER GROUPS

LOWER DENSITY IN LARGE RELEASES (I.E. >500 BIRDS)

>20% SHRUB COVER; >60% HERB COVER

<50HA

NO EFFECT

NO EFFECT

NO EFFECT

NO EFFECT

ROBERTSON 1988 SPARROWHAWK FOX TEMPORAL MONITORING

OF FOX ACTIVITY STOCKING DENSITY OF POULTS

LOWER DENSITY OF POULTS WITHIN PENS, OR

A NUMBER OF WIDELY DISPERSED PENS

ALLAN ET AL. 2000

BUZZARDS

UNIDENTIFIED

CORRELATION BETWEEN

RELEASE PEN HABITAT

VARIABLES AND

PREDATION

AGE OF PEN

VEGETATIVE COVER (ABOVE 1.5M)

YOUNGER PENS

HIGHER COVER

KENWARD 2001A

BUZZARDS

TAWNY OWLS

SPARROWHAWKS

CORVIDS

FOX

CORRELATION BETWEEN

RELEASE PEN HABITAT

VARIABLES AND

PREDATION

SHRUB COVER

TREE CANOPY COVER (PERCH AVAILABILITY)

STOCK DENSITY

HIGH SHRUB COVER

LOW CANOPY COVER

HIGH DENSITY


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6.3 Outdoor poultry units In comparison to the gamebird industry there was a paucity of available information on the extent and magnitude of the impacts of birds of prey on outdoor poultry units.

In Bresse, France, Stahl et al. (2002) undertook a field study (1999-2000) to quantify the overall levels of losses of free-range poultry to predators and to identify which species were involved in depredation. In this region, free-range poultry are reared according to strict rules set by law. Brooder farms sell 1-day old chickens to producers, who raise several flocks (typically 500 birds per flock) on separate fields. Chickens are retained in poultry house for a maximum of 35 days and then given free access to open ranges for 9-23 weeks (dependent on the category of chicken). In this region, Stahl et al.’s (2002) study involved 60 producers and included counts of chickens, searches for corpses, identification of predator signs at kills (feather, hair, scats and tracks) and examination of carcasses. In a sub-set of 27 producers, of 49,137 chickens in 69 flocks, 3081 had disappeared after 20 weeks and 1,352 had died from natural causes or disease. The loss to predators was estimated as 6.3%. Amongst all 60 producers, a total of 494 predation events were reported with 1,500 birds killed (97%) or wounded (3%). Overall, 70% of farmers lost poultry to predation and the range of losses per flock was 0-34%. Of 276 predation events investigated 52% were caused by avian predators and 28% by mammals (19% unknown and 1% conspecifics). However, mammals (7.3 chickens per attack) killed more chickens per predation event compared to avian predators (1.4 per attack) and accounted for the majority of chickens killed (68% versus 24%) (7% unknown and 1% conspecifics). Of 276 predation events, raptors were responsible for 22% of attacks (goshawk 1%, buzzard 0.4%, unknown 20.6%) and 10% of kills (goshawk 0.6%, buzzard 0.4%, unknown 9%). The comparative figures for crow were 9% and 4% and for fox 6% and 19% respectively. The estimated economic loss to predation for a typical 500-bird flock raised on 0.5 ha was 238 Euros or 119 Euros/ha. The 24% of total kills attributed to predatory birds corresponded to 29 Euros/ha. The 0.4% of known buzzard kills equated to around 5 Euros/ha (12 Euros for all known raptors). In comparison, the 19% of known fox kills represented 23 Euros/ha. The results contrasted with a previous mail survey in 1990 in the same area in which losses to predators was estimated to be 12% (double that in Stahl et al.’s [2002] field study). The results also contradicted the belief that raptors and corvids had a major impact on poultry. Farmers had attributed a large proportion of losses to raptors (40%) and corvids (23%). Farmers’ over-estimation of losses to avian predators was considered to be due to their being more likely to attack during the day, perching in the area, rarely removing prey from the site and eating prey in situ. Seventy percent of farmers reported losses to foxes. A comparative figure for avian predators was not presented. In the UK, members of the Poultry Keepers Forum have described attacks on chickens (pullets and full grown birds) in backyard collections by buzzards (The Poultry Keeper Forum 2007) (http://archive.thepoultrykeeper.co.uk/about10698.html).


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Buzzards have also been recorded taking offal at poultry farms (Schreiber et al. 2001). Historically, sparrowhawks have been reported to predate poultry units. Collins (1927) (cited in Baxter et al. 2007) found that the crop contents of 9 specimens examined contained 9.5% poultry. Ravens and other corvids were heavily persecuted in Britain in the late 17th and early 18th centuries because they were regarded as preying on farm poultry and young livestock (Jones 1972). The Pembrokeshire Bird Group (2006), on 19th February 2006, reported 188 ravens on a chicken farm, in Pembrokeshire, which were feeding on chicken waste. Similar to the gamebird industry, mammalian predators (principally foxes) have been implicated as the principal source of predation at poultry units rather than raptors. In mid-Wales, east midlands, and West Norfolk 49-78% of farmers (n=148) responding to a questionnaire survey reported suffering losses of poultry to foxes (Heydon & Reynold 2000). In north-west Wales, Staffordshire and Worcestershire, 28 of 335 farmers who responded to a questionnaire survey (n=1200) raised poultry (‘poultry – permanently housed’, ‘poultry – free range, ‘poultry or ornamental fowl’), 11% of whom reported having experienced predation by polecats (Packer and Birks 1999). The poultry industry appears to hold similar perceptions as the gamebird industry in respect to indirect effects of predation by birds of prey. Potential indirect effects are said to include deaths from ‘smothering’ that can occur when poultry mass within a paddock in response to perceived danger, or reduced production (e.g. suppressed growth of birds or egg laying) through increased stress due to predator presence. In a report on the welfare of laying hens, the UK’s Farm Animal Welfare Council (FAWC) state that ‘...wild birds flying overhead may induce a specific predator avoidance reaction, involving high levels of fear...’ and ‘...predators cause welfare problems both directly, causing injury and death and indirectly, by inducing fear...’ (http://www.fawc.org.uk/reports/layhens/lhgre023.htm).

The occurrence of indirect effects of predation on outdoor poultry units are similarly reported from the USA, for example: ‘...frightened birds can pile in a corner and smother each other...’ (Ison et al. undated). ‘...swooping birds may cause panic in poultry and serious injury or death to fleeing birds...’ (Bourne 2001). However, no information was found that empirically tested the extent and magnitude of any causative role of birds of prey in any indirect losses arising from their presence at outdoor poultry units.


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6.4 Sheep and lambs

6.4.1 Impacts of ravens

Ratcliffe (1997) reported MG Ridpath’s 1953 investigations for the Ministry of Agriculture and Fisheries into reports of lamb-killing in Pembrokeshire. In 100 hours of observation in a coastal region with five breeding pairs of ravens, he found no evidence of attacks on either ewes or lambs. In contrast, in an inland and upland area, during 220 hours observation he saw two lambs actually killed by ravens, and nine other attacks on lambs and eight on ewes. The success or failure of the attacks on lambs depended mainly on the vigour with which the mother defended her offspring. This upland area had three breeding pairs of ravens, but the attacks appeared to be perpetrated entirely from birds in a non-breeding flock, varying between nine and 19 in number. Ridpath emphasised that his limited observations could not be used to draw wider conclusions about the scale of the problem. Ratcliffe (1997) also reported observations by Ryves (1948) of solely benign interactions between ravens and sheep/lambs, with birds only feeding on dead lambs or placentas. Ratcliffe (1997) postulated that in many breeding areas there is sufficient sheep and lamb carrion at nesting time to satisfy the needs of the breeding pairs, removing any need for the birds to attack living animals. In contrast, non-breeding flocks may live in areas with more marginal food supply, or create heavy food demands upon their foraging areas. Together with other factors such as weather and condition of the animals may predispose the occurrence of attacks on lambs. Studies on other birds of prey have shown levels of lamb predation (as opposed to scavenging) to be minor compared to total losses to all causes (e.g. white-tailed eagle, Marquiss et al. 2003ab). Similarly, analysis of concurrently increasing UK raven populations and decreasing upland wader populations (1994-2007) indicated no significant negative spatial or temporal relationships between the abundance of ravens and five species of waders (Amar et al. 2010). Weak negative relationships between raven abundance and trends for two other species were considered to warrant further investigation. Such studies, however, have tended to focus on the activities of territorial breeding pairs. In recent years, in the UK, reports have described increased predation involving flocks of non-breeding birds, rather than territorial pairs. Outside of the historical observations (above) and current farmers’ anecdotes there has been no known attempt to quantify the extent and magnitude of predation by such non-breeding flocks of ravens in the UK. The only known quantitative study in Europe of raven predation on livestock was conducted in Germany during the 1990s (Brehme et al. undated). During the early 1990s, an increasing number of farmers in the Land of Brandenburg complained of losing sheep and cattle to ravens. Reports from farmers ranged from injuries to individual young animals to large-scale losses of young and adult animals. Among a number of initiatives in response to this situation, systematic scientific investigations into the causes, extent and effects of the occurrence of ravens in grazing flocks/herds was commissioned. A project working group was established that encompassed not only nature conservationists and scientists from the ornithological sphere, but also scientists, officials and association members from the agricultural centre. The studies involved a number of methods: - Questionnaire surveys of farmers (100 sheep farmers, 391 cattle farmers).


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- More detailed questioning of farmers who reported problems and assessment of rearing conditions (22 sheep farmers, 50 cattle farmers).

- Visits immediately after reports of damage (15 sheep farmers, 14 cattle farmers). - Behavioural observations (including filming) of the interactions between grazing animals

and ravens in flocks/herd were problems were reported. - Evaluation of deterrence measures. - Experimental shooting to scare the ravens. - Quantification of harmful effects and development of a key to determine the causes of the

damage. - Post-mortem examination of carcasses reported to have been killed by ravens. The key findings of the study: - 22% of sheep farmers reported damage (22 of the 100 surveyed; 51 replied). - 13% of cattle farmers reported damage (50 of the 391 surveyed; 207 replied). - Injuries and losses represented <1% of the total population of the suckler cow herds

involved in the survey, but with local variation. - Visits and detailed questioning, however, revealed cases where farmers admitted it was

not certain that animals had been killed by ravens, that said animals had been seriously ill and would have died anyway or simply the presence of largish flocks was perceived as threatening.

- In some cases, rearing conditions were such that they encouraged raven presence and damage by them, and surrounding conditions liable to promote this: dead animals not removed or deliberately left as diversionary food for ravens, obvious disease in the flock, open feeding (e.g. feed pellets) attractive to ravens, and the proximity of landfill sites, composting plants, ill-advised game-feeding stations or similar food sources.

- A number of fictitious ‘false positives’; though also some ’false negatives’ from farms not taking part in the survey suffering damage.

- Observations indicated that most contacts between ravens and animals were benign. Deliberate injury, sometimes from sustained attacks, was an exception involving diseased animals or unviable young, but occasionally also in young not protected by their dams. Ravens systematically tested the viability of the animals (mainly when asleep); but targeted pecking of healthy young ceased immediately when animals reacted. The behaviour of dams varied considerably and had a considerable influence on the duration and intensity of pecking.

- Ravens exploited risk situations leading to peck injuries in young animals and/or dams around birthing, or to diseased or handicapped animals. In some cases injuries inflicted may be serious with the risk of leading to death in animals which were ill or weak anyway. All animals which were injured by ravens had a previous history – either they were neglected or diseased young animals or dams who had difficult births, or were animals unable to stand. The killing of healthy animals was not observed.

- General conditions, in terms of livestock management, were considered to play a crucial role in the accumulation of ravens.

More recently, in Denmark, the focus of concerns has been raven predation on piglets at outdoor units (N. Kanstrup pers comm.).


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7. Review of management and control measures The documents on management and control techniques relating to birds of prey and livestock and details within, are presented individually in Appendix I and summarised in Appendix II. Deterrent techniques can be categorised into visual, auditory, chemical, exclusion, habitat modification and lethal. The aim of deterrent techniques is to prevent or reduce the utilisation of a vulnerable site or commodity by the target species, with no overt attempt to reduce the size of the overall population (other than potentially shooting a few individuals to aid scaring). Conversely, population control techniques seek to directly reduce the population, through lethal (e.g. shooting) or non-lethal means (e.g. fertility control). Mitigation measures can be targeted either directly at the bird of prey species in question or indirectly at the resources they utilise (e.g. prey or habitat). The following review of international literature on management and control measures categorises techniques into four non-mutually exclusive categories, defined by the target: - Measures targeted at birds of prey - Measures targeted at the habitat or environment - Measures targeted at the livestock resource - Measures targeted at other predators 7.1 Measures targeted at birds of prey

7.1.1 Visual deterrents

7.1.1.1 Lasers

As the demand for non-lethal, environmentally safe methods of bird scaring has increased, interest has grown in the use of lasers, particularly low-power lasers that work under low light conditions. The low power levels, accuracy over distance, silence and the ability to direct them on specific problem birds, makes laser devices an attractive alternative to other avian scaring devices. Birds are startled by the strong contrast between the ambient light and the laser beam. During low light conditions this technique is very selective, but at night the light beam is visible over a large distance and hence can cause non-selective disturbance. Low-powered hand-held lasers have been used successfully to disperse a variety of avian species from roosts (Glahn et al. 2001; Bradley et al. 2002). In the UK, use against two cormorant roosts had mixed results (McKay et al. 1999). The use of lasers can be an effective method of bird scaring. The equipment, however, is expensive and specialised training is required, adding to the costs. As the effectiveness of the laser decreases with increasing light levels, it is likely to be most effective at dawn and dusk. Its usefulness may therefore be confined to night-time roosts and feeding sites at dawn. Scaring with a laser could potentially be used in attempts to relocate birds of prey in cases where they habitually perch or roost close to livestock premises, during low light conditions but would require the presence of a trained operative.


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7.1.1.2 Human-scarer Human activity can disturb birds from specific areas either deliberately by direct harassment (Vickery and Summers 1992), or indirectly through, for example, leisure activities (Bell and Austin 1985, Owens 1976). Those sites where man is absent or rarely present, particularly on foot, such as airfields, are particularly attractive to birds. Human presence is a feature of many bird deterrent methods, and it should be appreciated that it is difficult to separate the effects of the device, e.g. pyrotechnics, from the effects of human presence. In the USA, human activity in lambing paddocks was considered to help alleviate livestock losses to eagles (Matchett and O’Gara 1987) and losses of poultry to hawks and owls (Hyngstrom and Craven 2005). Advice in South Africa considers that the presence of humans in the vicinity of a lambing flock was more effective than the presence of guard animals (donkeys, Anatolian dogs and other breeds) (Endangered Wildlife Trust’s Wildlife Conflict Prevention Group [undated]). A shepherd’s presence was advocated during the daily periods of main eagle predation activity, in this case early-morning, noon and late-afternoon. Bird of prey feeding activity may occur in the early morning when the cost of hiring staff to scare birds at such times of day would be high. It is also possible that in the absence of real danger (e.g. shooting) birds may habituate to the presence of people (Kirby et al. 1996).

7.1.1.3 Scarecrows

Scarecrows, are common, traditional methods used in attempts to scare avian species. They mimic the appearance of a predator and so cause birds to take flight to avoid potential predation (Harris and Davis 1998). Most scarecrows are human-shaped effigies, usually constructed from inexpensive materials. To maximise effectiveness devices should possess biological significance, appear life-like, be highly visible and their location changed frequently in order to extend the period of habituation (Vaudry 1979; Shivik 2004). The effectiveness of scarecrows may be enhanced if fitted with loose clothing and bright streamers that move and create noise in the wind (Vaudry 1979) - effectively becoming a moving visual. It has been suggested that where eagles are not habituated to humans, scarecrows may be used successfully (Matchet and O’Gara 1987). In the USA, human-like scarecrows suspended on ridges where sheep typically bed for the night seemed to cause golden eagles to avoid those areas (Matchett and O’Gara 1987). Also, scarecrows used in conjunction with harassment (pyrotechnic shells) seemed to be effective in deterring eagles away from lamb flocks (O’Gara et al. 1984 cited in Matchett and O’Gara 1987). Scarecrows are also advocated as an effective deterrent for repelling raptors when they are moved regularly and used in conjunction with shotgun fire or pyrotechnics (Hyngstrom and Craven 2005). O’Gara (1994) stated that scarecrows may keep eagles away from an area for up to three weeks; advice also includes shooting or shooting at ravens to maintain wariness in eagles. Also, in the USA, Beranger (2007) advocated the use of visual distractions, such as hanging old clothes in and around the edge of pastures to deter raptor (eagles, hawks, owls, black


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vultures Coragyps atratus and turkey vultures Cathartes aura) predation on flocks of Heritage Turkeys Meleagris Gallapavo. In contrast, in a survey of fishery hatchery managers in the United States only one of the 14 hatchery managers who commented on the effectiveness of various control techniques against cormorants said that scarecrows had a high success rate; six said they had no effect (Parkhurst et al. 1987). Some birds may even come to associate scarecrows with favourable feeding conditions (Inglis 1980). Ultimately, however lifelike, under most circumstances scarecrows do not present a threat that is sufficiently alarming to birds (Inglis 1980). Over a period of time birds learn that effigies or models do not represent an actual threat and are no longer alarmed by them. To increase the threat and, therefore, the habituation time, it is recommended that these devices be reinforced with other sound-producing or visual deterrents. Ideally, for example, scarecrows should be periodically reinforced by human activity. A successful example of the latter approach was used to successfully deter birds from crops in Israel (Nemtzov and Galili 2006).

7.1.1.4 Corpses

Deploying dead specimens or taxidermic effigies of the target species in a manner which signals danger to conspecifics has been used to disperse birds from areas. Initially birds often approach the corpse but often leave when they see the unnatural position of the bird. This approach has been frequently used in attempts to deter gulls from airports (Harris and Davies 1998). The reaction of herring gulls Larus argentatus and ring-billed gulls Larus delawarensis to conspecific taxidermic models varied dependent on the circumstances (Seamans et al. 2007). The models were ineffective when placed in a highly desirable location (e.g. nest sites and the active face of a landfill) and alternative areas were not readily available. When placed in desired loafing areas away from food sources, however, gulls relocated to alternative areas and avoided loafing areas with effigies for an extended time. It was concluded that effigies enhanced the dispersal of gulls when used as part of an aggressive, integrated management program. In the USA, black vulture roosts on communication towers have been dispersed by hanging a vulture carcass or taxidermic effigy in the roost (Avery et al. 2002). Likewise, roosts of turkey vultures have been deterred from a disused rocket test-firing tower by a taxidermic model turkey vulture (Seamans 2004). Placing the model in an upside-down hanging position was more effective than placing the model in a supine position. Cattle egrets Bubulcus ibis shot at a heronry and placed in clear view around the roost repelled other egrets and prevented other birds from landing; after the dead birds were removed the flock landed immediately (Fellows and Paton 1988). Conversely, carcasses and effigies were not effective in deterring carrion crows Corvus corone or Canada geese Branta Canadensis (Naef-Daenzer 1983; Seamans and Bernhardt 2004 cited in Seamans et al. 2007).


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7.1.1.5 Eyespots Eyespot patterns are a commonly used deterrent, either painted onto a substrate or on devices such as balloons and kites. These patterns are images of eyes composed of a small circle (the ‘pupil’) centred in a larger circle of another colour (the ‘iris’). The basis for their use is the same as for predator models: mimicry of real predators; though they may also mimic the eyes of conspecifics, which may be alarming as many avian species have frontal threat displays in which the eyes are prominent (Inglis 1980). Laboratory studies have shown that eyespot patterns can induce an aversive response in birds (Inglis et al. 1983). Two circular eyespots arranged horizontally, each containing concentric rings of bright colour appear to be the most alarming. Those that have a three-dimensional appearance may enhance the effect, and large eyespots are better than small ones (Inglis 1980). Inglis et al. (1983) concluded that simple eye patterns could deter starlings Sturnus vulgaris from foraging within their vicinity; effectiveness was dependant on a distinction between ‘pupil’ and ‘iris’. Habituation to eyespots, however, was rapid. McNamara et al. (2002) found that ‘eyes’ painted on the black plastic which covered silage bales reduced damage to the bales by 65%. Painted eyespots have been used in attempts to deter sparrowhawks from racing pigeon lofts. In a questionnaire survey of Scottish Homing Union members, 21% of respondents (n = 86) reported eye-spots to be at least partially effective in preventing sparrowhawk attacks on pigeons at the loft (Henderson et al. 2004).

7.1.1.6 Balloons

Balloons tethered in a crop have been used as an inexpensive method of bird deterrence, but studies show that they are not very effective and birds quickly habituate to them. To increase the effectiveness of balloons eyespots can be printed on the side. In the USA, Beranger (2007) advocated the use of visual distractions, such as hanging balloons in and around the edge of pastures to deter raptor predation on flocks of Heritage Turkeys.

7.1.1.7 Kites

Kites and kite-hawks (kites that simulate birds of prey) work as mobile predator models, which birds perceive as a threat. The kites bear an image of a soaring raptor and are tethered to the ground. Conover (1983) (cited in Harris and Davis 1998) tested four designs of hawk-kites, but none effectively deterred birds from feeding on corn. To be effective, kite-hawks need to be ‘flown’ beneath helium balloons in order to possess sufficient ‘threatening’ movement (Conover 1984). When this was done, the kites became more effective at scaring birds from the cornfields. Helium-filled bird scaring kites have been deployed between dawn and dusk at landfill sites. Numbers of gulls, corvids and starlings on sites remained relatively unchanged and there was little evidence that birds were deterred from the sites (Baxter 2002).

7.1.1.8 Radio-controlled aircraft

Radio-controlled model aircraft have been used to scare or ‘haze’ birds since the early 1980s, mainly over airfields (Smith et al. 1999), but have also been used over agricultural areas, fisheries and landfill sites. This method has been shown to be very effective and birds habituate more slowly to a treatment in which they are being actively hazed.


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Although an effective method of bird deterrent, using this technique is labour-intensive and requires skilled operators; at Whiteman AFB, training of model aircraft operators can take two months (Hibler 1999). Model aircraft cannot be used in inclement weather.

7.1.1.9 Lights

Flashing, rotating, strobe and searchlights are a novel stimulus to birds, which encourage an avoidance response (Harris and Davis 1998). Although a steady light source such as searchlights have been known to attract birds at night, particularly when it is cloudy or foggy (Harris and Davis 1998), strobe lights, revolving lights and amber barricade lights might be useful for deterring night-feeding birds such as herons at fisheries (Littauer 1990, Nomsen 1989 cited in Kevan 1992). The lights have a blinding effect that causes the birds to become confused and restricts their ability to fish (Salmon et al. 1986 cited in Kevan 1992). However, birds can quickly become habituated and black-crowned herons have been known to avoid the glare by landing with their backs to the lights (Kevan 1992). Although lights are easy to deploy and require very little maintenance, they should not be used where they might cause a visual nuisance to neighbouring properties. They may not be effective during daylight hours and their ability to scare birds at night varies with the bird species. Lights are best used with other deterrent methods.

7.1.1.10 Mirrors/reflectors

Mirrors and reflectors work on the principle that sudden bright flashes of light produce a startle response and drive the bird from an area. However, the response of free-living birds to mirrors has been investigated in only a handful of species. Mirrors and reflectors have been used in attempts to deter sparrowhawks from racing pigeon lofts. In a questionnaire survey of Scottish Homing Union members, 33% of respondents (n=86) mirrors/reflectors to be at least partially effective in preventing sparrowhawk attacks on pigeons at the loft (Henderson et al. 2004). Kenward (1999), however, stated that there is no clear evidence of success for the use of mirrors against raptors. Although easy and inexpensive to put up and easy to relocate, the effectiveness of mirrors and reflectors as a bird scaring technique is variable. As they are only effective when they reflect sunlight and so are useless before sunrise (Nakamura 1997), they are best combined with other methods of scaring.

7.1.1.11 Tapes

Suspended tapes as a scaring device act as a combination of visual and exclusion deterrence. They are easy to erect and a wide selection of twines and tapes are readily available. Reflecting tape such as Mylar tape has been used in attempts to deter birds in a number of circumstances. The tape has a silver metal coating on one side that reflects sunlight and also produces a humming or crackling noise when moved by the wind. A variety of birds have been deterred by tape suspended in parallel rows over ripening crops (Bruggers et al. 1986).

7.1.1.12 Flags, rags and streamers (fladry)

Fladry is a method where strips of fabric are hung from cords or fences and strung to encircle pastures or areas that need protection. The movement of the flag or rag in the wind is perceived as a threat by predators, which then avoid the area. Electrified fladry combines


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fabric with electric fencing, a technique that attempts to establish conditioned avoidance to fladry (Shivik 2006). In the USA, fladry is generally used against mammalian predators, such as wolves and coyotes. The effectiveness of fladry against avian predators is considered limited (Shivik et al. 2003 cited in Shivik 2006).

7.1.2 Auditory deterrents

Auditory deterrent devices include gas cannons, pyrotechnics, bio-acoustics, acoustics, ultrasonics and high intensity sound. In addition, there are numerous low-tech methods for producing sounds, such as tin cans and chains. The application of auditory deterrents (indeed to a lesser extent also some other categories of deterrents) requires careful consideration, as there is the potential to disturb the stock they are meant to protect in addition to scaring predators.

7.1.2.1 Gas cannons

Gas cannons (or ‘exploders’ in the USA) are mechanical devices that produce loud banging noises by igniting either acetylene or propane gas. Their scaring effect is probably related to the similarity of the noise to that of a shotgun. The unexpected bang produced causes a ‘startle’ reflex and promotes escape flight (Harris and Davis 1998). Gas cannons are commonly used to scare birds off agricultural crops; they have also been used at fisheries to deter cormorants. Their effectiveness, however, is variable and is dependent upon the method of their deployment, the bird species involved and the availability of alternative feeding areas. Broyer et al. (1993) found that cannons were effective on small fisheries, but not on large bodies of water. Habituation seems to be the main reason for their loss of effectiveness; a cannon firing repeatedly without any variation in timing or direction quickly loses its potential to scare birds. Moving the cannon every few days is recommended (NFU undated; Transport Canada 1994; Harris and Davis 1998; Gorenzel et al. 1994), along with variable firing intervals (Harris and Davis 1998).

7.1.2.2 Pyrotechnics

Pyrotechnics include a wide variety of noise-producing cartridges usually fired from rockets or rope bangers, or on aerodromes from modified pistols or shotguns, which produce a loud bang and emit flashes of light. They include shell-crackers, screamer shells and whistling projectiles, exploding projectiles, bird bangers and flares. Cartridges are projected from a shotgun with a range of 45-90m, or pistol (range approximately 25m), and then explode. Pyrotechnic-charged cartridges (e.g. Bird Frite®) provide a combined visual and aural stimulus. A pyrotechnic shell is fired from a conventional 12-gauge shotgun, which produces a small report when the trigger is pulled, and a much louder report when the shell explodes after leaving the gun. The explosion of the shell produces a bright flash and smoke. Most species of birds immediately take flight in response. Best practice is to aim the shell so as to burst a few metres from the target birds (e.g. Anon [undated]). Using 12-gauge blanks in amongst the more expensive pyrotechnic cartridges can reduce the costs of this technique. In the USA, loafing black vultures and turkey vultures reportedly, can be dispersed from pastures using pyrotechnics (Avery and Cummings 2004). The effect was only short-term, however, with vultures returning to the site within a few hours. In Montana, USA, harassment


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of problem eagles with explosive charges, an airplane and playback of taped distress calls failed to alleviate livestock losses (Matchett and O’Gara 1987). Also, in the USA, pyrotechnics are advocated for deterring hawk and owl predation on poultry and small game – the most commonly used are shell crackers (Hyngstrom and Craven 2005). Also, used are noise, whistle and bird bombs; these are fired from a pistol and are less expensive than shell-crackers, but their range is shorter. Pyrotechnics have proved effective in dispersing birds at some airports, landfill sites and agricultural sites (reviewed in Harris and Davis 1998). The effect on cormorants, however, dispersed from aquaculture facilities is relatively short term (hours to a few days) (Draulans 1987). Kenward (1999) stated that there is no clear evidence of success for the use of shell-crackers against raptors.

7.1.2.3 Shoot to scare

As an alternative to the use of pyrotechnics (above), in the USA, loafing black vultures and turkey vultures reportedly, can be dispersed from pastures by firing .22 caliber or larger rifle ammunition or shotguns nearby (Avery and Cummings 2004). As with pyrotechnics the effect was only short-term, with vultures returning to the site within a few hours. Harassment with non-lethal projectiles, such as rubber bullets or paint-balls has been suggested (Shivik 2004, 2006). The benefit of this technique would be that it is selective for predators presenting an immediate threat of depredation. The technique, however, would be limited in its practicality due to the logistics of requiring a trained operative to be ready to observe and harass the predator. Also, due to the proximity required, the predator is likely to develop an aversion to the person rather than the projectile. Keller and Vordermeir (1994) found that scaring cormorants by shooting with blanks was effective at reducing bird numbers when used in combination with crackers and other pyrotechnics. However, Broyer et al. (1993), Barlow and Bock (1984) and Littauer (1990) report that such techniques rarely deter cormorants for long periods. In a large scale replicated field experiment no lesser scaring effect of shooting blanks compared to shooting to kill was detected; however, differences between shoot to kill and blank sites may have contributed to this lack of difference in effectiveness (McKay et al. 1999; Parrott et al. 2003).

7.1.2.4 Bio-acoustics and other acoustics Bio-acoustic deterrents are sonic devices that transmit sounds of biological relevance: recorded bird alarm and distress calls. In general, alarm calls are given when birds perceive danger, whilst distress calls are vocalised when birds are captured, restrained or injured. These calls are species-specific and can cause conspecifics to take flight. Alarm and distress calls, however, may also evoke a response in other species that are taxonomically related to the call-producing species (Baxter et al. 1999) or which closely associate with it. Responding to alarm/distress calls has high survival value, therefore such biologically meaningful sounds are more repellent and more resistant to habituation than other sounds (Bomford and O’Brien 1990, Harris and Davis 1998). However reactions to distress calls can vary both with the species and the individual bird (Schmidt and Johnson 1983); in some groups such as gulls, alarm/distress calls initially act as an attractant with birds approaching the source, apparently to investigate, before flying away (Brough 1968).


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Auditory systems using bio-acoustics are often considered the most effective as they act on the birds’ instinct to avoid danger (but see Bomford and Sinclair 2002). Their effectiveness is determined by the use of species-specific calls and the availability of alternative areas to move to. Although such systems can be placed in a resource location on a random timer sequence, birds will quickly habituate to such a device if it is not frequently moved, and it may cause noise nuisance in adjacent areas. A manually-operated system that is used only when birds are present will be more expensive but will also be more effective and less likely to become a nuisance. With all systems, sound transmission will be influenced by ambient temperature, wind direction and reflections from surrounding features such as buildings, and such factors need to be taken into consideration when siting sonic devices. Success requires high-quality recordings of suitable calls and specific calls changed frequently (Bomford and Sinclair 2002). As with most methods of bird control, an integrated approach using a variety of techniques is likely to be more effective and reduce habituation rates (Schmidt and Johnson 1983). Sonic systems that produce a variety of electronically-produced sounds are also commercially available. The range of loud and sudden noises they produce can frighten birds but as they have no biological meaning the risk of habituation is great (Harris and Davis 1998). With static systems, frequent changes in location and adjustments to the sounds can reduce habituation (Harris and Davis 1998). There is no evidence that ultrasonic devices deter birds (Bomford and O’Brien 1990). In fact, evidence indicates that most species of birds do not hear in the ultrasonic range (>20kHz) (Erickson et al. 1992, Harris and Davis 1998) and so there is no biological basis for their use. In the USA, sonic devices have been tested and shown little benefit in preventing or reducing eagle predation (O’Gara 1994). For example, in south western Montana, USA, the use of distress call tapes did not alleviate livestock losses to eagles (O’Gara 1983 cited in Matchett and O’Gara 1987).

7.1.2.5 Radio- and movement-activated electronic guards These devices use disruptive stimuli to scare predators, typically acoustic and strobe lighting devices that operate only when activated by a trigger mechanism. Radio-activated devices have been used with some success on bald eagle Haliaeetus leucocephalus and turkey vultures (Shivik 2006), although habituation occurred within weeks. To work it is necessary to fit the potentially offending predators with transmitters. This could be prohibitively difficult for wild birds but may work with birds on a captive release program. Alternatively, movement activated guards can be used that use passive infrared sensors to detect approaching predators.

7.1.3 Diversionary feeding

Deploying diversionary (decoy) or sacrificial food is a technique used to divert feeding birds away from the susceptible resource. The provision of supplementary or ‘buffer’ prey has been used in a number of circumstances in attempts to reduce raptor predation.


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In some countries, to protect racing pigeons, buffer prey in the form of less valuable birds is established in additional lofts, to reduce the predation risk of high value birds (JNCC 2000). In Portugal, it was postulated that lofts of low-value rural pigeons could be established in those Bonelli’s eagles territories with depleted natural food resources to act as a diversionary food resource to reduce predation on both game and racing pigeons (Palma et al. 2006). In Australia, placing animal carcasses away from stock paddocks is advocated for reducing predation on lambs by wedge-tailed eagles (DEC 2007b). Shooting to scare around stock is also advised so that eagles move to the undisturbed area with the carcass. In the UK, at pheasant release pens, the provision of an alternative food source was suggested to be effective in reducing predation by sparrowhawks (Lloyd 1976a) and buzzards Buteo buteo (Harradine et al. 1997). Hinsley and Redpath (1996) reported the establishment of pigeon lofts on grouse moors in attempts to protect grouse from peregrines. In England, the predation rate in a colony of little terns Sterna albifrons, decreased when the two pairs of resident kestrels Falco tinnunculus were provided with supplemental prey (dead mice) (Durdin 1993). However, supplementary feeding of peregrines Falco peregrinus, had little success during attempts to protect a roseate tern Sterna dougallii colony (Avery & Winder 1990). Supplementary feeding of hen harriers, in Scotland, did not increase the density of nesting harriers but reduced the number of grouse chicks taken by fed birds compared to unfed birds (Redpath et al. 2001). Reduced predation, however, was not followed by increased autumn density of grouse. Feeding added 11% to management costs and for it to be adopted as a practical solution for alleviating raptor predation a proven beneficial effect on grouse bags was deemed necessary. Subsequently, diversionary feeding scored highly amongst both grouse managers and raptor conservationists when evaluating a range of hen harrier management options (Redpath et al. 2004). On Mull, recommended measures to reduce white-tailed eagle predation on lambs included the use of feeding sites in late winter to encourage eagles to nest as remote as possible from lambing areas (Marquiss et al. 2003a). There is evidence that raptors preying on livestock are more likely to be immature birds that are less adept at capturing healthy natural prey and may more readily resort to domestic prey in times of food stress (Murphy 1977). Under such circumstance, supplementary feeding of young birds may alleviate predation. The British Association for Shooting and Conservation’s (BASC) policy advocates that all steps should be taken to support the current diversionary feeding trials of raptors, and other potentially useful measures, on grouse moors (BASC 2009). There is a potential risk in providing supplementary food, which is that in the long-term it may lead to an increase in predator-density, if prey availability is limiting predator numbers (Shivik 2004). Supplementary food may also increase the survival rates of young birds and exacerbate the long-term problem. In Sweden, goshawk range size was smaller and breeding density higher in areas rich in rabbits than elsewhere (Kenward and Marcstrom 1981). In one such area goshawk predation on wild pheasants was particularly high (Kenward 1982, 1986). It was suggested that the predation on pheasants was exacerbated by the abundance of rabbits drawing more hawks into the area than would normally have occurred in such a habitat.


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A further concern, for some, over diversionary feeding is that it is considered wrong in principle – turning the countryside into a zoo; this argument, however, has been considered difficult to sustain in view of the fact that farmers are paid to grow bird seed crops, feeders are put out for pheasants and members of the public feed wild birds (Tapper 2007).

7.1.4 Bird of prey removal

7.1.4.1 Translocation

In a BASC survey of its gamekeeper membership 11% of respondents (n=996) wished to see troublesome individual raptors caught and relocated elsewhere (Harradine et al. 1997). Translocations have been used as a management tool for many decades, including for raptors. Early translocations were mainly for hunting purposes whilst in more recent times conservation reasons have been the primary focus (Cade 1986). At present, translocations are still extensively used for conservation purposes but they are also increasingly employed in wildlife management to remove ‘problem’ animals. A recent review of mammal translocations found a gap in knowledge concerning whether translocation of problem animals actually does resolve human-wildlife conflicts (Massei et al. 2010). The review concluded that where one or few animals were removed, the problem was deemed to be resolved, even though the animals could-re-offend in the new area and the problem might still occur in the original area through the removal of the wrong individuals or because replacement animals became ‘problem’ individuals. For group translocations there was little evidence that translocation resolved the problem. Relocation of goshawks has been used widely in Sweden (Kenward 2002). The use of spring-nets on pheasant kills permitted the selective capture of juvenile birds (80% of the total birds captured) that were responsible for killing pheasants. Young birds tended to accumulate in areas of high prey density after dispersal rather than breeding adults (Marcstrom & Kenward 1981). Translocation of the birds showed that few birds returned after being moved more than 30km (Marcstrom & Kenward 1981). It was recognised, however, that as most hawks removed were juveniles, their non-return may have been due to their unfamiliarity with the areas. More wide-ranging species may require much greater translocation distances (Kenward 2002). Marcstrom & Kenward (1981) concluded that transporting goshawks for release more than 30km away was a viable alternative to killing them in order to reduce hawk numbers at a site, but was unlikely to have much effect on the goshawks in a country where the population is at environmental carrying capacity. In Texas, trapping and relocation of black vultures has proved ineffective. Relocating trapped birds did not reduce problems at the site at which they were trapped. Furthermore, there were increased complaints regarding vultures at the release sites (Avery and Cummings 2004). In Florida, four of eight vultures (fitted with transmitters) translocated >250km from their trap site were tracked to within 16km of their original roost (Avery and Cummings 2004). In the USA, translocation of golden eagles has proved largely inneffective. In Wyoming, of 14 resident golden eagles that were translocated over 400km, 12 returned to their capture sites within 11-316 days (Phillips et al. 1991; Linnell et al. 1997). The vacant territories were taken over by non-territorial birds within a mean of three days. In Montana, the translocation of 432 golden eagles between 1975 and 1983 had little demonstrated effect on


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reducing depredation on livestock. In South Dakota, the translocation of 19 sub-adult golden eagles (>322km from the capture site) did reduce predation on farms at the capture sites (Waite and Philips 1994) but the long-term affect was not reported. In the USA, recommended traps for hawks and owls include Swedish goshawk trap, bal-chatri trap, spring traps and sliding padded pole trap (Hyngstrom and Craven 2005). Kenward (1999) advocated setting spring-traps on kills as capture would be selective on raptors taking poultry or game. In South Africa, 42 eagles (black eagle Aquila verreauxii, crowned eagle Stephanoetus coronatus and martial eagle Polemaetus bellicosus) were translocated. Five of eight eagles for which subsequent movements were known returned, from distances between 28km and 105km, to their former ranges (Boshoff and Vernon 1988 cited in Linnell et al. 1997). In Scotland, one proposal to help resolve the red grouse/hen harrier conflict was to manage harriers so that any nests in excess of a fixed quota (allocation or ceiling) based on an agreed nesting density would be removed (Tapper 2007). It was suggested that if fertile eggs were removed from such nests they could be used as part of a translocation programme to speed population recover. The proposal did not gain much support from either grouse managers or conservationists. Removal experiments have been undertaken on sparrowhawks in Scotland. In one study, seven female sparrowhawks were removed from different nesting territories, and seven males from seven other territories (Newton and Marquiss 1991). Three of the seven removed females were replaced 12-16 days later, with all three replacement females laying eggs. Three (or possibly four) of the seven removed males were replaced 14-28 days later, but only one of the pairs with replaced males laid eggs. Removed birds were ‘...released in June...’ implying that they were temporarily held in captivity. Information on the fate of translocated sparrowhawks is available from a recent study in Scotland that attempted to explore the effectiveness of two management options (translocation and reflective tape) for reducing the frequency of sparrowhawk attacks on racing pigeons in the immediate vicinity of the loft (Humphreys et al. 2010). A total of seven sparrowhawks (two adults and five immatures) were captured at five lofts. Each bird was fitted with a radiotransmitter (battery life of nine days) and released a minimum distance of 30km from the loft. One adult sparrowhawk returned to the loft (distance 86km), was recaptured and returned close to the loft (distance 87km) on the second occasion. Within the short radio-transmission life span of there was no obvious tendency of the other sparrowhawks to return to the loft, based on locations by date. At two lofts more than one sparrowhawk was captured – an adult female followed by an immature female. The latter indicating that removed individuals can be quickly replaced by other birds. For the study as a whole, it was not possible to draw conclusions on the effectiveness of the two management options due to insufficient sample sizes (lofts), issues over experimental design and the limited amounts of observational data collected at lofts. Several reviews concerning the capture and removal or translocation of raptors have been published (Linnell et al. 1997; Cade 2000; Fischer and Lindenmeyer 2000). The general consensus suggests that whilst translocation can be an effective tool for conservation, particular with regard to re-introduction, capture and removal to resolve human-wildlife


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conflicts is mostly unsuccessful. Typically the problem is simply transferred elsewhere or only temporarily resolved until the removed animals either find their way back and return to their old haunts or are replaced by their neighbouring conspecifics. An important consideration in translocation is the welfare of the relocated individuals. Translocations may have a detrimental impact on survival rates and lead to extreme dispersal (Massei et al. 2010). Although Massei et al.’s (2010) review of translocation dealt with mammals, the issues and concerns raised are also applicable to other taxonomic groups, including birds. Potential risks associated with translocation are that stress-related capture can result in mortality, homing may cause animals to leave the release area, individuals may suffer from malnutrition, dehydration, decreased immunocompetence and predation, and the spread of disease. A key decision when considering translocation to reduce conflict is whether there is any real benefit in moving individuals of a species that is at carrying capacity in all areas in which there is suitable habitat (Kenward 2002). In translocations an integral element of success should be the resolution of the conflict (Massei et al. 2010).

7.1.4.2 Lethal control

In the USA, selective lethal removal of specific problem vultures was considered as potentially contributing to resolving local vulture management conflicts (Avery and Cummings 2004). Federal and state laws protect all hawks and owls. However, the United States Fish and Wildlife Service (USFWS) may issue shooting permits for problem hawks and owls if non-lethal methods of controlling damage have failed or are impractical and if it is considered that killing the offending birds will alleviate the problem (Wade et al. 1984, Wade 1986; Hyngstrom and Craven 2005). In California, USA, shooting and poisoning with DRC-1339 (3-chloro-p-toluidine hydrochloride) baited eggs was used to reduce raven predation on juvenile desert tortoises (Butchko 1990). DRC-1339 is an avian toxicant reported to cause non-violent death hours after ingestion; corvids exhibit high susceptibility to the toxicant. Control efforts reduced a population of 125 ravens to approximately ten. In Oregon, a population of 200 ravens was reduced by 90% through baiting near sheep carcasses with DRC-1339-treated cubed meat (Larsen & Dietrich 1970). The toxicant was also administered using DRC-1339 solution injected into the eyes of sheep carcasses. The raven population had been reported as causing high mortality to newborn lambs and blinding ewes. In Denmark ravens are a problem at outdoor pig rearing facilities, where they can predate piglets. It is possible to get a permit to kill a certain number of ravens in specific cases. But even that is known to be rather inefficient as the raven populations in some areas are very dense and the birds quickly find ways of adapting (N. Kanstrup, pers comm.). In Germany, during the 1990s, ravens were causing problems to extensively grazed sheep and cattle Brehme et al. undated). Experimental measures to deter the birds included shooting to scare. Otto (2000) (cited in Brehme et al. undated) showed that such measures were largely ineffective. Even an identified raven that had been shot at returned on the field near to where it had been shot at as early as 14 minutes later.


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In Finland during the early 70s, an average 5,800 goshawks were killed each year (Moilanen cited in Marcstrom and Kenward 1981). It was estimated that 31% of Finnish juvenile goshawks died in this way (Saurola 1976 cited in Marcstrom and Kenward 1981). This estimated level of cull did not appear to reduce the Finnish goshawk breeding population (estimated at 10,300 pairs) (Marcstrom and Kenward 1981). In Sweden, during the same period, ‘thousands’ of goshawks were killed each year (Haukioja and Haujioka 1971 cited in Marcstrom and Kenward 1981), particularly at pheasant farms (Marcstrom and Kenward 1981). The Swedish breeding population was estimated independently at 3,500-13,600 pairs (Marcstrom and Kenward 1981) and 10,000 pairs (Svensson 1979 cited in Marcstrom and Kenward 1981). It was also estimated that no more than 18% of Swedish juveniles were being killed each year. Overall, however, the EU Concerted Action REGHAB Project concluded that very little is known about the effect of culling on raptor populations (Vinuela and Arroyo 2002). It was also concluded, however, that in some countries there is a need for efficient and selective methods of legal predator control, to replace invasive, non-selective and illegal methods commonly used (particularly poison). In Britain, a BASC survey of its gamekeeper membership revealed that 25% of respondents (n=996) wished to see a cull of raptors and 14% the licensed removal of troublesome raptors (Harradine et al. 1997). BASC has recommended that an immediately-responsive licensing system be put in place, by appropriate government agencies, for the destruction/translocation of specific problematic raptors, their nests or eggs, for those situations where serious damage cannot otherwise be prevented (BASC 2009). As a last resort, it has been advocated that removal should be considered as conservation can suffer if serious predation problems are ignored (Kenward 1999). Respect can be lost for conservation laws, and birds may be killed anyway – but unselectively. Concerning the strict protection of raptor populations, Kenward (1999) raised the point that, although an important tool, if treated as an ideology it can also promote damaging conflicts. Under the Wildlife and Countryside Act (1981), licences can be issued to take a small number of birds for the purpose of preventing serious damage. Licensing authorities, however, need to balance the need to safeguard populations of formerly declining (often through persecution) predatory species, whilst also addressing the concerns of stakeholders. The effectiveness of predator removal may be influenced by what components of the predator assemblage are controlled. Removal of only selected, larger species can allow increases in the populations of smaller predators - termed ‘mesopredator release’ (Crooks & Soule 1999). Such mesopredator release may result in no decrease, or an increase, in overall predation rate. A reversal of competitive release has also been observed where a larger species (raven) was freed from constraints imposed on its distribution and behaviour by a smaller species (hooded crow Corvus cornix) (Bodey et al. 2011). On Rathin Island, off Northern Ireland, ravens ranged more widely and the predation of artificial nests was significantly higher (although total predation was similar) after the removal of crows.

7.1.4.3 Egg-oiling

Egg destruction is used to reduce the local population of pest birds and in the UK it requires a licence from Natural England. Eggs can be destroyed by several methods. Straight-forward


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egg removal can encourage re-laying unless the eggs are replaced by hard-boiled or wooden replicas (Baker et al. 1993). The pricking of eggs with a needle allows bacteria to enter the egg as well as desiccate its contents (French and Parkhurst 2001), but some pricked eggs may still hatch, and birds may abandon clutches to relay. Egg oiling is a cheaper, more effective and more humane method of egg control. It involves coating the egg shells with oil such as liquid paraffin (Baker et al. 1993). This stops air from passing through the shell to the embryo and prevents it from developing properly. Baker et al. (1993) tested this method on Canada geese and achieved a 100% success rate; none of the 231 treated eggs hatched. Some eggs were also pricked and these too did not hatch, but they were incubated for significantly less time, allowing the adults to relay elsewhere. This technique, using white mineral oil, was also effective on ring-billed and herring gull eggs, though some eggs (8-9%) sprayed early in incubation or sprayed with only a small quantity of oil late in incubation, did hatch (Christens and Blokpoel 1991). For total success, it was recommended that spraying should be undertaken three times during incubation. Although this should be more effective it is more labour-intensive and so less cost-effective. The sole use of egg destruction is unlikely to reduce a local population in the long-term. It is a time-consuming process as all nests have to be located and treated, and this may be hindered by problems of access. The timing of destruction is important and any reduction in a population caused by the loss of young birds may well be offset by immigration of new birds from nearby non-treated areas.

7.1.5 Chemical deterrents

7.1.5.1 Taste repellents

Taste repellents can be divided into primary and secondary repellents. Primary repellents are agents that are avoided upon first exposure because they smell or taste offensive or cause irritation. Secondary repellents are not immediately offensive, but cause illness or an unpleasant experience following ingestion that the bird relates to the taste of the treated-food (Conditioned Taste Aversion - CTA). In future encounters the bird will avoid the treated food. Secondary repellents are usually regarded as the more effective form of deterrent.

7.1.5.2 Primary repellents

Primary repellents are usually derived from natural products including food and flavour ingredients (Sayre and Clark 2001). A considerable amount of research has been carried out in the USA into the use of chemical taste repellents such as methyl-anthranilate (ReJeX-iT®), anthraquinone (Flight Control™), and methiocarb, with varying levels of success. O’Gara (1994), however, states that no repellents are registered or effective in reducing eagle predation. Although registered and in use as general bird repellents in the USA, they are not registered for use in the UK.

7.1.5.3 Secondary repellents Conditioned Taste Aversion is generated through a subconscious association between taste and a feeling of illness experienced after ingesting food. It is a natural phenomenon that has evolved in many vertebrates to prevent poisoning. CTA can be generated deliberately in an animal by the addition of an undetectable illness-inducing chemical (e.g. lithium chloride) to


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a specific foodstuff, thus causing the animal to associate the taste of that food with illness (Wilbanks, undated). Cowan et al. (2000) recognised the possibilities of applying CTA to the issue of reducing predation carried out by species of conservation concern, e.g. raptors. The removal of a sensitive prey species from the raptors diet would reduce the perceived threat from and consequently reduce persecution of the raptor species. Cowan et al. (2000) identified factors that determined the strength and persistence of aversions and constraints on effectiveness. The optimal time between the exposure to the conditional stimulus and the onset of illness appears to be between one and six hours. Although the type of chemical additive influences the CTA (Gill et al. 1999), in general tastes that are preferred appear to generate more robust CTA. The strength of the CTA is related to the strength of the illness, the intensity of the taste stimulus and also by the novelty of the taste stimulus. For many species gustatory cues (odour, colour) other than taste can also induce aversion; the effect is stronger, however, if aversion is simultaneously associated with taste. In a practical setting, effective inducement of CTA relies on the aversive treatment being delivered to the predator in a way that cues associated with the prey are incorporated into the aversive learning process. In addition, effective conditioning requires that predators not only reject food at the consumptive stage of feeding but also at the preceding prey seeking and capture stage; that is, CTA needs to invoke ‘avoidance at a distance’. The establishment of CTA, therefore, is a similar process to the natural processes that produce forms of aposematism, notably Batesian mimicry. Conditioned Taste Aversion has been found to be long-lasting in various mammals (e.g. Nicolaus et al. 1989a, 1989c) but has not been extensively researched in birds (Nicolaus et al. 1989b). However, CTA has successfully been induced in avian predators. Egg predation by crows Corvus brachyrhynchos on artificial nests was significantly lower following aversive conditioning using Landrin treated chicken eggs, but remained unchanged at sites were no conditioning occurred (Dimmick and Nicolaus 1990). Aversion was retained in conditioned sites the following year without further treatment. CTA has also been induced in a guild of egg predators (avian and mammalian) that included ravens and magpies Pica pica (Coates et al. 2007). Captive cormorants were conditioned to avoid trout Salmo trutta, aversion persisting for seven months without reinforcement (McKay et al. 1999). In an experiment on captive American Kestrels Falco sparverius Nicholls et al. (2000) found that food treated with methyl-anthranilate and 4-aminoacetophenone was not always rejected. Furthermore, a second study that used a combination of the chemical additives with food dyed an unfamiliar colour suggested that the colour and not the chemicals was the most aversive agent. In California, USA, a study on aversive condition of ravens to protect Least tern eggs showed that successful conditioning (using methiocarb) was dependent on site-specificity and the availability of natural untreated eggs (Avery et al. 1995). Ravens avoided treated surrogate eggs at a simulated tern colony but resumed taking tern eggs in the natural colony. When exposed to treated surrogate eggs placed within the natural colony, ravens also avoided tern eggs. Aversive conditioning was also dependent on ravens encountering only treated eggs (as opposed to untreated natural eggs) frequently enough to discourage exploratory behaviour.


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In the UK, the application of CTA to deter raptor attacks on racing pigeons has been investigated (Musgrove 1996). In 1994, Musgrove identified a chemical (methyl anthranilate) that was aversive to falcons when presented on meat but appeared benign to pigeons when applied to their plumage. Field-testing of the technique, however, was very limited, due to reluctance among fanciers to volunteer their pigeons for use in trials (Musgrove 1998). The field data available, however, indicated the technique was promising. Peregrines resident in the Cheddar Gorge appeared to be deterred from taking racing pigeons (A. Musgrove reported in JNCC 2000). Also, a fancier who used the chemical, and whose loft was situated in sight of a peregrine eyrie, considered that the technique might well have been effective (Musgrove 1998). It was considered that the technique required further development to ensure that the chemical was not only effective but also completely safe to pigeons and fanciers. At the time and its current state of development, and specifically in view of health and safety issues, the Scottish Homing Union (SHU) felt that it could not advocate the technique (SHU 1998). The history of the application of CTA in the field has produced equivocal and controversial results. On the one hand claims of reduced predation in large-scale field trials have been criticised for lack of adequate experimental controls. On the other hand, dismissal of CTA following failure to produce an effect has been criticised for using inappropriate doses or presentation of bait; effectively failing to ensure that essential criteria of the conditioning process were met.

7.1.5.4 Behavioural repellents

Behavioural repellents or ‘frightening agents’ such as Avitrol (4-aminopyridine) can be classed as toxicants rather than repellents as in large enough doses they are lethal (Harris and Davis 1998; Mason and Clark 1997). In sublethal doses they cause disorientation and erratic behaviour and birds often emit distress calls. This behaviour frightens the other non-intoxicated birds from the resource; the aim of invoking this effect (area repellency) is to reduce damage caused by the treated flock with minimum mortality. When used as a frightening agent the Avitrol is applied in diluted bait with only a relatively small proportion of the bait particles treated. Such behavioural repellents are not licensed for use in the UK.

7.1.5.5 Tactile repellents Tactile repellents involve the use of sticking substances that discourage birds because of their ‘tacky’ feel. They can be applied as clay-based seed coatings, or as pastes and liquids on ledges and other roosting structures to deter settling birds. Tactile repellents to deter perching contain polybutene and may contain other substances to induce a chemical reaction that gives the bird a mild ‘hot foot’ (Transport Canada 1994). Such ‘hot foot’ repellents are not licensed for use in the UK.

7.1.5.6 Repellents in the UK

In the UK, at present, only two chemicals are registered by the Pesticide Safety Directorate of Defra for use as bird repellents – Ziram, product name Aaprotect and Aluminium ammonium sulphate (marketed under several product names). These products, however, are for use to protect a variety of crops (R. Watkins, pers. comm.).


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7.2 Measures targeted at the habitat or environment

7.2.1 Exclusion

7.2.1.1 Netting

The use of nets to cover resources and totally exclude birds is considered one of the most effective bird deterrents. It is used to prevent birds from feeding on high value crops such as cherries, blueberries and grapes (Grun 1978; Biber and Meylan 1984 both cited in Harris and Davis 1998). Complete enclosure of ponds also effectively prevents cormorant predation of fish (e.g. Salmon and Conte 1981). In the USA, hawks and owls may cause damage by predating on poultry or small game (Hygnstrom and Craven 2005). A number of techniques are advocated for alleviating damage. Exclusion measures include housing poultry at night or, if this fails, installing fenced enclosures covered with poultry wire, nylon netting or overhead wires. Netting the roof on large experimental enclosures has successfully excluded raptors (Krebs et al. 2001 cited in Kenward 2002) but roofing would negate the role of release pens in allowing birds to leave when they can fly well enough to clear the sides of the pen. Although netting has proved effective for crop protection (Stucky 1973; Foster 1979) the cost of materials and perceived difficulty in erecting and removing the netting has discouraged many stakeholders from adopting this method (Fuller-Perrine 1993). In the USA, however, Tilman et al. (2000) concluded that where losses to birds are regular and substantial, it is likely that a cost-effective netting scheme could be devised; particularly if costs are spread over the lifetime of the net. In Australia, economic analyses indicated that netting can be cost-effective for high-value resources even when damage levels are not significant; but not for low-value resources (DEC 2007a). A potential hazard of netting is bird mortality, which can be high with flexible netting (Twedt 1980 cited in Fuller-Perrine 1993); stiffer material, however, is less prone to entangle birds (Fuller-Perrine 1993).

7.2.1.2 Suspended lines/tapes

Overhead wires or lines strung over the area from which birds are to be excluded can be an effective deterrent, and a less expensive method than full exclusion. A number of factors are believed to influence the effectiveness of tapes and lines in deterring birds, including the coverage and configuration of lines, the size of the bird species, attractiveness of the site and the availability of alternative resources. Studies investigating the effectiveness of suspended tapes or lines in deterring birds from crops have provided mixed results (Pochop et al. 1990). In some cases where lines were ineffective, large spaces between rows of tapes may have allowed birds to avoid the tapes and enter the crop (Tobin et al. 1988; Conover and Dolbeer 1989). In Italy, to protect pheasants in release pens from raptors (particularly buzzards) coloured tapes (or wires) are stretched at 2-3 meters intervals across the open top pen at discrete points


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at which predation more often occurs (e.g. near corners, over feeders). In some cases this has been considered effective by game managers (F. Santilli, pers comm.). In the Heritage Turkey industry in the USA, advice to protect poults from raptors includes suspending strands of fishing line (spaced at two foot intervals) above pens; the barrier can be made more visible by attaching lightweight streamers or pieces of cloth (Beranger 2007). Although a close configuration of tapes may be successful in terms of resource protection, it can interfere with husbandry or maintenance activities and increase costs in terms of labour and materials. Close rows of tapes protecting the resource can increase the costs, and even if predator damage is reduced the technique may not be cost-effective. Prediction of the magnitude of potential resource loss and the corresponding financial value, therefore, is necessary to inform stakeholders when the deployment of measures to deter birds becomes cost-efficient.

7.2.2 Habitat manipulation

7.2.2.1 Natural and artificial cover

The use of natural and artificial cover in poultry pens has been applied overseas. In the Heritage Turkey industry in the USA, the American Livestock Breeds Conservancy advocates the provision of cover in pastures, in the form of trees or shrubs or shelters (Beranger 2007). In addition to protection from predators, livestock products raised under woodland systems demand a market premium (McLean et al undated). For example, chickens reared under the French Label Rouge system (woodland and pasture) attract a higher premium than free-range birds both in France and abroad. The nature and extent of cover has also been identified as an important factor in lower raptor predation at pheasant release pens (see section 9).

7.2.2.2 Perch availability Natural roosting substrate can be made less attractive to birds by thinning or pruning vegetation (Booth 1994). In the USA, advice to prevent predation of poultry and small game by hawks and owls includes eliminating perch sites within 100 yards of the threatened area, by removing isolated trees and other perching surfaces (Hygnstrom and Craven 2005). Also, advocated was the installation of utility lines underground to obviate the need for telephone poles near poultry-rearing sites. The foraging techniques of some raptors include sitting and watching for potential prey from exposed perches. An absence of suitable perches (through removal) overlooking livestock premises may lead to reduced likelihood of predation; removal of perches is also advocated at artificial feed sites for game birds (Kenward 1999). Removal of perches from sensitive areas could be supplemented with the creation of alternative perches away from livestock areas. Further, eagles could be encouraged to use the new perch sites through the provision of decoy food in the vicinity of the new perches.


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7.2.2.3 Anti-perching devices In circumstances where perches cannot be removed anti-perching devices can be used. These prevent birds from perching, roosting and nesting on surfaces and ledges and involve wires, gels, coils or point systems. All either prevent physical access or else provide an unstable surface for perching. Installing a thin wire over the perch, which prevents the bird from landing is probably the simplest method. All these designs may help to deter perching birds but their success is dependent on all perches being treated to discourage birds from the area. In the USA, advice to prevent hawk and owl predation on poultry and small game includes the use of anti-perching devices such as capping poles with sheet metal cones or fitting spikes (Hyngstrom and Craven 2005). In the USA, five commercial perch deterrents proved to be ineffective in preventing raptors and corvids (including raven) from perching on support poles for power distribution lines, due to inherent design and placement flaws (Prather & Messmer 2010).

A recent introduction into the UK is Bird Free® Optical Gel a product that is marketed as an anti-perching treatment. The gel is deployed in shallow saucers arranged in a sequence along a preferred perching substrate (e.g. ledge). Deterrence is claimed to be achieved through utilising the birds visual spectrum (that includes ultraviolet) with the product giving the appearance of fire to the birds (so acting as a visual deterrent rather than a tactile one).

7.2.2.4 Screening

Screening crops involves deploying vision barriers, either natural or artificial, that prevent birds having a clear line of sight; the technique is used against cockatoos in Australia (DEH 2007). When used in combination with other habitat manipulations screening was effective in deterring galahs from a wheat field (Jarman and McKenzie 1983). In a similar manner, it may be possible to screen vulnerable livestock areas to reduce their being over-looked from vantage points utilised by birds of prey.

7.2.2.5 Zoning

Zoning is a concept that has recently been examined and involves the physically separation of predators from livestock (Shivik 2004). Some areas would be managed to be predator free and designated for livestock, whilst other areas would be designated places where predators would be free to roam with minimal human disturbance. Success of this concept would depend on identifying the appropriate sites and sizes of zones and buffer areas such that conservation needs are met (Linnell et al. 1996 cited in Shivik 2004). In Spain and Scandinavia zoning with quotas has been established for large carnivores. Zoning involves areas where protection of the predators remains absolute and other areas where licenses may be granted to remove animals (Kenward 2002). The principle behind zoning is that management of control is retained in a situation where socio-economic pressures may result in illegal and unregulated management. Removal of predators to agreed quotas could involve either lethal (shooting) or non-lethal methods (translocation), targeting of specific age groups (e.g. juveniles) or production of young (e.g. egg removal or oiling). An important consideration with quotas is the possibility that areas with reduced protection (i.e. with permitted removal) may act as population sinks for mobile species, such as raptors.


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7.2.2.6 Manipulation of natural landscape vegetation In discussing raptor predation problems, Kenward (1999) pointed out that agricultural intensification tends to remove cover and presumably increases prey vulnerability. Also, by reducing or concentrating natural sources of food and/or providing artificial supplementary sources, prey activity and aggregation may increase, thus attracting predators. Improving cover at feed sites and approaches and removing nearby perches for raptors were recommended. For some prey animals, vulnerability to predation by raptors could be reduced by encouraging the growth of more cover in their natural habitat. The effect of available cover has been investigated on the susceptibility of red grouse to predation by hen harriers and peregrine falcons (Thirgood et al. 2002). It was found that although some habitat characteristics increased the likely rate of prey encounter it did not influence the strike success for harriers. In France, research showed that strips of tall cover could become ‘traps’ for partridges in winter by concentrating both prey and predators on small isolated areas (Bro et al. 2005), Further research has been recommended to identify efficient habitat management schemes (Bro et al. 2005). Whitfield (2000) argued that eagle predation on lambs could be reduced through retaining or enhancing the natural live prey of eagles. This could be achieved by habitat management but also by a reduction in stocking levels. Whitfield (2000) suggested the latter strategy would reduce the number of carcasses to scavenge and this would reduce the density of eagles, however, the abundance of natural prey would also increase the breeding success of the remaining pairs. When considering landscaping it is necessary to be sure that links between landscape and predation are causal (Kenward 2002). It is also necessary to consider whether habitat management is likely to have consequences for other aspects of biodiversity. 7.3 Measures applied to livestock

7.3.1 Design of livestock units

In the USA, to reduce the probability of ‘smothering’ events in outside pens as a result of birds piling up when frightened, it is advocated that all right-angled corners in pens are eliminated through modification using wire, plywood boards or metal sheeting (Bourne 2001).

7.3.2 Livestock practices

Livestock practices could be altered to reduce the exposure of vulnerable animals in certain areas or during critical periods (Shivik 2004, 2006). Lambs are especially vulnerable when they have gained enough age and confidence to distance themselves from their mother ewes (Warren et al. 2001). To counter this risk lambs could be kept indoors until they have matured to a size/weight that reduces their attractiveness as prey. Alternatively, lambs could be moved indoors during periods of the year when eagle predation is most likely to be greatest, i.e. during the eagle breeding season when food demands are greatest due to rearing offspring. Taken to the extreme, if livestock are bred earlier in the season, young will be larger earlier and less vulnerable to predation (Shivik 2004). Raising the standard of


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husbandry so that more lambs are reared may also help compensate for losses to eagles (Whitfield 2000). In the USA, it is considered that vulture depredation can be prevented by locating lambing, pigging and calving activities in sheds or buildings, or by using paddocks close to barns or buildings with human activity so that birthing animals can be monitored closely (Avery and Cummings 2004). Advice in the USA to alleviate eagle (bald eagle and golden eagle) predation on livestock includes livestock practices, such as: confining stock in buildings and pens, avoid putting lambs and kids out to pasture until they are several weeks old, graze lambs in pastures with brushy and wooded areas that provide cover, use close herding, carry out lambing and kidding indoors, shift the lambing and kidding season and remove carrion (O’Gara 1994). In the Heritage Turkey industry in the USA, The American Livestock Breeds Conservancy, advocates delaying the introduction of young birds to pasture until they are 10-12 weeks old and large enough to be less attractive to raptors (Beranger 2007). In Australia, measures to reduce predation by wedge-tailed eagles include coinciding lambing with neighbours, so that eagles are not attracted to one area (DEC 2007b). Also, the use of small, well-sheltered lambing paddocks near the homestead are considered beneficial in a number of ways - ewes are present to defend and feed lambs, lambs are kept warm and farm activities scare off birds. Penning sheep during lambing was considered effective protection against eagles (Murphy 1977). In Sweden, in mid-winter, ring-necked pheasants are sometimes caught and penned to ensure the survival of breeding stock through the late-winter period when Northern goshawk predation on wild pheasants tends to be most intense (Kenward 1999). In Norway, sheep farming is carried out with a combination of indoor winter feeding, grazing on fenced farmland during spring and autumn, and summer grazing on outfield open range pastures (Asheim and Mysterud 1999 cited in Asheim and Eik 2005). Predation during outfield pasturing increased between the late 1980s and early 2000s. The most cost effective mitigating measure was considered to be shortening the outfield-grazing period. In Namibia, there has been a return to the tradition of gathering livestock into kraals for overnight protection (Davies 1999). In South Africa, the use of camps, kraals and night enclosures is also advocated as a long-term (albeit expensive) solution to raptor conflict on farmland by the Endangered Wildlife Trust’s Wildlife Conflict Prevention Group (undated). In Scotland, Scottish Natural Heritage advice to deter ravens from predating lambs includes, where possible, housing of ewes giving birth (SNH 2009b). On Mull, one of the recommendations to reduce white-tailed eagle predation on lambs was to keep lambs remote from eagles - recognised as impractical on most of Mull (Marquiss et al. 2003a). In one case, however, shelter, in the form a poly-tunnel has been provided during lambing. The most positive management, however, to increase lamb production was


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considered to involve removing those factors predisposing lamb predation and deaths from other causes through improvement of ewe nutrition and reducing tick infestation (Marquiss et al. 2003a). Wade (1980) noted that, in general, husbandry practices can reduce predation but various environmental factors can prevent their use. They are often least effective or most difficult to apply on open range, large pastures and dense woodland or scrub.

7.3.3 Close shepherding

In South Africa, it has been recognised that small improvements in sheep flock management may be far more beneficial to productivity than large-scale attempts to control predators (Davies 1999). The simplest and most effective method has been to place a shepherd with the flock during the lambing period. Another option employed by many farmers is to move their lambing flocks away from areas of eagle activity such as nests. Removal of lamb carcasses from lambing areas is also undertaken. On Mull, in Scotland, recommendations to reduce white-tailed eagle predation on lambs included management trials to determine the cost-effectiveness of deterring eagles from lambing areas using close-shepherding (Marquiss et al. 2003a). This advice is reiterated by Scottish Natural Heritage to deter ravens from predating lambs (SNH 2009b).

7.3.4 Prompt removal of fallen or unhealthy stock

The prompt removal of any fallen stock will reduce the attractiveness of livestock holdings to birds of prey and other predators, both avian and mammalian. A subsequent reduction in the visitation rate of predators will decrease incidents of further predation. Stock exhibiting signs of ill health should also be promptly removed to indoor premises; removing one category of vulnerable animals to predators. In the USA, removal of dead livestock and road-killed animals reduces food availability and is considered to lessen the likelihood of vultures being attracted to an area (Avery and Cummings 2004). In Willamette Valley, USA, the abundance of sheep carrion was considered the primary factor influencing bald eagle wintering abundance (Marr et al. 1995). It was suggested that sheep carcasses could be scattered in areas away from lambing pastures to minimise conflicts between sheep producers and eagles. Scavenging of fallen stock by raptors may, however, be beneficial in a broader-scale, as such carcasses may attract other potentially more regular predators. This was the case in two of the releases of red kites Milvus milvus in Scotland. The concerns of gamekeepers on adjacent land about predation of game birds were not borne out, with kites proving themselves as useful scavengers of dead pheasants that had previously attracted foxes (Marquiss et al. 2003a). This contrasts with pheasant release pens where recommendations are to leave carcasses in the pen, so that a returning raptor can feed on the carcass as opposed to killing another poult (Ashmole 1987; BASC undated). Carcasses left in pens, however, should be placed off the ground so as not to attract mammal predators.


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7.3.5 Guard animals

A guard animal is any animal that, when placed, with a flock, represents a threat to predators (McNeal undated). Dogs, llamas and donkeys have all been used as guardian animals (Andelt 2004, Alberta Sheep and Wool Commission 2007). Each species has its advantages and disadvantages and vary in their effectiveness dependent on the species of livestock being guarded and the habitat. For example, dogs were regarded as more effective in deterring mammalian predators on open ranges and fenced pastures, whereas llamas and donkeys appeared most effective in fenced pastures <300 acres (Andelt 2004). Mason (2001), however, states that there is little or no evidence that donkeys are effective guardians. In the USA, guard dogs have been used successfully to haze geese (Woodruff and Green 1995) but are most often used to protect sheep and are now incorporated into western US sheep production. A study has shown that domestic sheep producers with livestock guard dogs lost smaller proportions of lambs compared to producers without dogs; losses of ewes, however, were similar (Andelt and Hopper 2000). Guardian animals are traditionally used against mammalian predators, particularly coyotes (Franklin and Powell 1994); little data is available on their effectiveness against avian predators, such as eagles (O’Gara 1994). Andelt and Hopper (2000) report figures for eagle (likely Aquila chrysaetos) predation for four sheep producers with guard dogs and one producer without dogs of 446 and 40 lambs respectively. O’Gara (1994) suggested that, to prevent eagle predation, guard dogs would probably be more effective in small pastures than in large pastures and open range conditions. Also, in the USA, a study on the cost-effectiveness of guard dogs concluded that 73% of livestock producers (mostly sheep) experienced estimated annual savings as a result of using guard dogs (Green et al. 1984). It was concluded that guard dogs appeared to offer a reasonable, low-impact method of deterring predation. It was, however, noted that not all dogs are effective, and dogs would not solve all predator problems. Sheep producers also used a range of other methods to alleviate predation (Green et al. 1984, Green et al. 1994), including shepherds, fencing, night-confinement, shed lambing and scare devices (Green et al. 1994). Beranger (2007) cites the findings of a survey of ranchers, in the USA, who used llamas to protect goats, cattle and poultry. Llamas decreased annual predation rates by 40-60% on poultry ranches. In 78% of cases, predation dropped to zero following the introduction of a llama. In the USA, an interview of 145 sheep producers with guard llamas revealed that before producers obtained their llamas, mean losses to predation were 26 sheep per year, or about 11% of their flock (Franklin and Powell 1994). After obtaining their llamas, losses decreased to a mean of eight sheep per year, or around one percent of their flock. Small flocks of geese, kept in the same enclosure with smaller poultry have been used successfully to deter hawks (including red-tailed hawks) (Beranger 2007). Guard animals are also advocated in South Africa, where donkeys Anatolian dogs and others are used (Endangered Wildlife Trust’s Wildlife Conflict Prevention Group [undated]). The presence of humans in the vicinity of a lambing flock, however, was considered to be more effective than guard animals.


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In the Heritage Turkey industry in the USA, The American Livestock Breeds Conservancy, report that some producers have suggested that raptors hunting poultry are often deterred if the birds are ranging with larger animals, such as sheep. Combined livestock operations, such as mixing sheep and cattle have also been advocated; sheep may receive some degree of protection in that cattle may be more aggressive to small predators (Shivik 2004). 7.4 Compensation and incentive schemes Where wildlife conflict exists between stock and predators of conservation concern, compensation or incentive schemes may be used.

7.4.1 Compensation schemes

Compensation schemes involve direct payment for livestock taken; usually incorporating a proportionate drop in value as not every individual taken will reach slaughter weight. Overseas, there is variation between countries in the approach to making payments to land managers whose income may be considered to be affected. For example, in Norway (D. Halley pers. comm.) compensation payments for golden eagle predation commenced about ten years ago. Payment is made for 'assumed damage', i.e. it does not have to be proved – proof is difficult in a country where sheep and reindeer are left unsupervised in remote areas for long periods. The scheme is considered to be potentially open to politically or financially motivated interpretations. In Finland (K. Norrdahl pers. comm.), the system differs for ‘normal’ livestock and for freely roaming reindeer, because the cause of death is seldom clear if a reindeer carcass is found weeks after the death. For livestock killed by large predators the full value is paid to the owner. Previously only the amount exceeding 250 euros was compensated but the system has recently changed. A benefit attributed to compensation schemes is that they increase tolerance towards wildlife and promote more positive attitudes and support for conservation among people most affected (Wagner et al. 1997). Compensation schemes, however, suffer from a number of disadvantages, including inflated or fraudulent claims, difficulties in distinguishing predated from scavenged losses and increased running costs associated with dealing with these issues. As predation issues are unlikely to disappear, a compensation programme also requires a sustained and sufficient source of funds. Further problems arise with the issue of indirect losses, from impacts on stock productivity, development and welfare. Nyhus et al. (2005) identified that even in circumstances where rapid and accurate verification of losses and adequate payments was possible, a compensation programme was still faced with difficult issues. For example, if compensation is available for losses, some stakeholders may be less inclined to adopt new or improved management practices that would alleviate conflict in the first place. In addition to these practical problems, on a sociological level compensation schemes reinforce the perception of a predator as a ‘problem’ from the outset.

7.4.2 Incentive Schemes

Incentive schemes offer payments that act as an inducement to reward landowners for undertaking actions that benefit wildlife and/or the environment, including actions that are likely to reduce the human-wildlife conflict. In the UK, examples of incentive schemes are the Mull Eagle Scheme and West Coast of Scotland Sea Eagle Scheme which promoted white-tailed sea eagles as an asset to those regions.


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The Mull Eagle Scheme (SNH 2004) (now superceded), was part of SNH’s Natural Care Scheme, offered support to hill farmers on Mull who had sea eagles and/or golden eagles on their land. The scheme was developed by SNH in consultation with Mull farming representatives. The scheme offered incentive payments towards positive management activities, such as extra shepherding. The development of the Scheme’s payment rates was based on ‘profit-foregone’, i.e. for costs that would not otherwise have been incurred. Some other payments (e.g. for sheep health) were direct contributions to the costs of materials, such as the purchase of a poly-tunnel lambing shelter.


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Table 7.1 Summary of potential techniques for the management of predatory birds on stock – measures targeted at PREDATORY BIRDS.

TECHNIQUE Application Benefits Costs

Scaring – visual and auditory

Lasers, human-scarer, scarecrows,

corpse, eyespots, balloons, kites,

radio-controlled aircraft, lights,

mirrors/reflectors, tapes, fladry.

Gas-cannons, pyrotechnics, shoot

to scare, bioacoustics, acoustics.

- Various visual and auditory devices.

- Most effective when used in combinations.

- Individual techniques are mostly relatively

cheap.

- Continual scaring with rotation of techniques in

combination can become expensive.

- Noise (e.g. gas cannons) and visual disturbance

to stock.

- Safety issues (e.g. pyrotechnics) with some

techniques.

- All techniques suffer from habituation.

Diversionary feeding

- Alternative attractive food source is supplied

away from the stock area.

- Can be supplemented by scaring at the stock

area.

- Retain carcasses of killed poults within release

pen but raised off ground onto post.

- Can be used to encourage birds of prey to

relocate away from stock areas.

- Can target problem individuals.

- Returning raptor will feed on carcasses as

opposed to making a further kill.

- Sacrificial food must be continually available

during the potential risk period.

- The additional food may increase the

attractiveness of the wider area to birds of prey

and other predators if supplied in too large a

quantity and over too long a period.

Chemical –

Conditioned Taste Aversion (CTA)

- CTA-treated stock bait is presented to birds of

prey.

- CTA has been shown to persist following a

single application.

- Technique requires development; outcome

unknown.

- High costs of licensing a chemical agent.

- Requires repeat applications for untreated

offspring.

Translocation of birds of prey - A number of potential capture techniques are

available, including a spring-trap set at a kill.

- Can remove birds from the sensitive area and

relocate at a distance.


- Relocated birds may return.

- Vacated territory may be occupied by new

bird/s.

- Suitable unoccupied areas for release may be

unavailable.

Relocation of birds of prey nest

sites

- Render preferred nest site unattractive so that

birds relocate further from area with

vulnerable stock.

- Provide diversionary food in vicinity of

alternative more remote nest site.

- Can attract birds from the sensitive area and

relocate at a distance.


- Outcome unknown.

Lethal control - Removal (e.g. shooting) of specific problem

birds (under licence).

- Immediately removes the problem.


- Regular removal may reduce the bird of prey

population.

- Potential for removed bird to be replaced by

another that has potential access to the same

stock.


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Table 7.2 Summary of potential techniques for the management of bird of prey impacts on stock – measures targeted at HABITAT MODIFICATION.

Target Application Benefits Costs

Netting

- Enclose stock areas with temporary or

permanent netting.

- At release pens create: (i) small fully enclosed

pens into which poults are first released, or (ii)

connected fully enclosed and open sections,

with poults moved into the enclosed section at

night.

- Effective and long-term.

- Will also exclude other predators.

- High initial capital outlay.

- Not economical unless predation frequent.

- Requires maintenance.

- May obstruct husbandry practices.

Suspended lines/tapes - Suspend overhead wires above vulnerable sites

within stock area.

- Effective and long-term.

- Will also exclude other predators.

- High initial capital outlay.

- Requires maintenance.

- May obstruct husbandry practices.

Live vegetative cover

- Provide sufficient herb cover (≥60%) and hard

woody cover (≥20%) in release pens.

- Provide woodland cover in poultry units.

- Provides visual and physical refuge for

threatened birds.

- Has an ecological basis.

- Initial capital outlay

- May interfere with husbandry practices.

Cut vegetative or artificial cover

- Provide shelters/refuges in the form of brash

piles or wigwams.

- Provide wooden shelters/refuges.

- Place within pens and at locations vulnerable to

predation outwith pens (e.g. feeding sites).

- Provides visual and physical refuge for

threatened birds.

- Initial capital outlay

Eliminate right-angled corners of

pens

- Build new pens with curved ‘corners’ or modify

the corners of existing pens.

- Removes potential locations for birds piling up

or smothering events. - Initial capital outlay

Manipulation of perch availability

- Remove/modify preferred perching sites in the

vicinity of stock (e.g. at pens and feed sites).

- Provide new/artificial perches in location away

from stock.

- Can supplement the attractiveness of new

perches with diversionary food.

- Reduces opportunities for birds of prey to

observe stock.

- Opportunities will be site-specific.

- Tree removal may be undesirable from

biodiversity and aesthetic perspectives.

- Preferred perches may be abundant.

Anti-perching

- If birds of prey habitually loaf on structures that

cannot be removed, install devices such as

wires, metal cones and points.

- Deters birds of prey from preferred perches.

- Reduces opportunities for birds of prey to

observe stock.

- May relocate to distant perches.

- Technique may require development to

determine most effective devices.

- Preferred perches may be abundant.

Zoning - Separate birds of prey from stock by buffering

predator-free and predator-tolerated areas.

- Reduces opportunities for interaction with

stock.

- Uncontrolled/removed birds of prey may move

into ‘predator-free’ area.

- Limited application if a high density of

gamebird estates/livestock units.

Manipulation of natural vegetation - Manage natural vegetation to increase wildlife. - Increased wildlife provides more abundant

natural prey for birds of prey.

- Higher natural prey density may attract and

retain birds of prey in the area; potential to

interact with stock.


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Table 7.3 Summary of potential techniques for the management of birds of prey impacts on stock – measures targeted at STOCK PRACTICES.


Lambing indoors - Transfer breeding animals indoors for births.

- Use of poly-tunnels if no suitable buildings.

- Removes the most vulnerable animals from

predation risk.

- Poly-tunnels temporary.

- Opportunities/practicalities to house animals

indoors will be site-specific.

- Costs of supplementary feed.

- Potential for increased disease.

Retain young indoors for longer

- Retain young indoors until large enough to be

at lower risk of predation.

- Release older pheasant poults.


predation risk.



- Potential increased disease risk.

Stock food - type and delivery - Use stock food type and delivery that reduces

spillage/waste.

- Reduces scavengers (e.g. corvids, gulls), which

in turn may reduce attractiveness of site to

large raptors.

- Opportunities for altering food type and

delivery are limited.

Close shepherding - Place a shepherd with the flock during lambing

time. - Effective and long-term.

- Cost implications.

- Require trained staff.

Removal of fallen/unhealthy stock

(lambs)

- Remove fallen stock as soon as possible.

- Transfer to indoors stock showing ill health as

soon as possible.

- Removes scavenging opportunities for birds of

prey and other predators.


predation risk.



Retention of dead/killed poults

(pheasants)

- Retain carcasses of killed poults within release

pen but raised off ground onto post.

- Returning raptor will feed on carcass as

opposed to making another kill. - May attract other predators.

Guard animals

- Dogs, donkeys and llamas have been kept with

stock to deter mammal and bird predators; also

geese.

- Guard animals can react to presence of

predators.

- High initial investment in terms of

purchasing/training guard animals.

- Little evidence for effectiveness against large

raptors.

Enhance stock welfare - Provision of nutritional supplements to

enhance stock condition.

- Reduced losses to disease.

- Lower incidence of losses and carcass

availability may decrease attractiveness of the

site to predators/scavengers.

- Costs of additional treatments.

Stocking levels

- Release lower number of stock into release

pens/rearing areas.

- Spread ‘standard’ stock number between

increased numbers of rearing areas.

- Reduced stress will lead to a decrease in losses

to ill health and disease.

- Reduced carcass availability may decrease

attractiveness of the site to

predators/scavengers.

- Reduced impact on vegetation will enhance

retention of protective cover.

- Greater survival rate will off-set losses to

predation.

- Reduced stock levels may decrease numbers of

stock reared/produced.

Breed of stock - Raise breeds with appropriate predator

response behaviour.

- Breeds that seek shelter rather than freezing in

the open will be more likely to avoid predation.

- ‘Optimal’ anti=predator behaviour may not be

associated with ‘optimal’ productivity (e.g. egg

production in poultry).


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Table 7.4 Summary of potential techniques for the management of birds of prey impacts on stock – measures targeted at OTHER PREDATORS.


Scaring – visual and auditory

Lasers, human-scarer, scarecrows,

corpse, eyespots, balloons, kites,

radio-controlled aircraft, lights,

mirrors/reflectors, tapes, fladry.

Gas-cannons, pyrotechnics, shoot

to scare, bioacoustics, acoustics.

- Various visual and auditory devices.

- Most effective when used in combinations.

- Reduces scavengers (e.g. corvids, gulls) visiting

the site, which in turn may reduce

attractiveness of the site to birds of prey.

- Greater all round benefit of reduced overall

predation.

- Continual scaring with rotation of techniques in

combination can become expensive; noise (e.g.

gas cannons).

- Noise (e.g. gas cannons) and visual disturbance

to stock.

- Safety issues (e.g. pyrotechnics) with some

techniques.

- All techniques suffer from habituation.

Lethal control - Shooting, trapping (e.g. crow trap, Larsen trap).

- Reduces scavengers (e.g. corvids, gulls) visiting

the site, which in turn may reduce

attractiveness of the site to birds of prey.


predation.

- Potential disturbance to stock, e.g. shooting.

Stock food - type and delivery

- Use stock food type and delivery that reduces

spillage/waste.

- Reduces scavengers (e.g. corvids, gulls), which

in turn may reduce the attractiveness of the

site to birds of prey.


predation.

- Reduced losses of food to scavengers.

- Opportunities for altering food type and

delivery are limited.


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8. Measures currently used in the UK Many of the mitigation measures identified in the review of international literature are currently, or have previously been deployed at pheasant release pens and/or livestock rearing areas in the UK. 8.1 Gamebird release pens

8.1.1 Measures targeted at predators

8.1.1.1 Deterrents Raptor attacks at release pens mostly involve tawny owls, sparrowhawks and buzzards, with pheasants most affected (Lloyd 1976a; Harradine et al. 1997). Gamekeepers have deployed a wide variety of deterrents in attempts to ameliorate raptor predation. Lloyd (1976a), however, found that deterrents were used primarily against foxes and any effect that they had on birds of prey was secondary. The techniques included: hangers (suspended paper and plastic sacks), various lights (storm lanterns, red roadside warning lamps, and orange and yellow flashing road lights, fladry and mirrors. Scarecrows were sometimes used both inside pens and in nearby rides. Nitrate bangers were used by some estates near the pen. More recently, to assist the UK Raptor Working Group, BASC undertook a survey of its gamekeeper membership to determine their problems with raptors and how they dealt with them. Information provided by almost 1,000 gamekeepers was subsequently assessed (Harradine et al. 1997). The survey revealed that most (c.84%), but not all, keepers affected by raptors took one some form of preventive measure. Many different deterrent and scaring techniques were used, either in isolation or combined, e.g. bangers, gas guns, alarms, hangers (i.e. loose items suspended above the pen) and mobiles, lights, mirrors, radios, owl decoys, scarecrows and human presence. The survey concluded that the ‘...most widely used scaring measures are reported to have varying and generally low levels of success...’ and ‘...with little apparent benefit...’. However, these conclusions seem to be pessimistic in contrast to data presented in Harradine et al. (1997). Estimated values from graphs summarising the reported use and success of scaring devices indicate that for ‘scarers’, the percentage of gamekeepers reporting at least partial success (i.e. ‘success’ + ‘partly successful’) was: sparrowhawk (n=184 gamekeepers) = 41%; buzzard (n=129) = 51%; tawny owl (n=160) = 61%; goshawk (n=43) = 37%. The report also provided the following, less pessimistic (for some species) summaries for the effectiveness of deterrents against each of the main raptor species: - ‘Sparrowhawk: Scaring mainly used but is only partly successful and involves mainly hangers and

other scaring devices....’

- Buzzard: Again mainly scaring which is relatively more successful than for sparrowhawk and

involving again mainly hangers and other scarers, but a certain amount of alternative feeding

and pen protection with some measure of success.

- Tawny owl: Scaring mainly used and generally successful with its taking the form mainly of

hangers and lights. As with the preceding species pen protection is reported as being of value.

- Goshawk: Scaring with hangers is mainly used but is hardly successful at all.’


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The Raptor Working Group concluded that there was no consistent application of deterrents at pheasant release pens, some of the most commonly used were those which appeared least successful, whilst some of the apparently most successful were less frequently used. Field trials were recommended to address the urgent need to assess the effectiveness of different deterrent measures (also recommended in Harradine et al. 1997); subsequently field trials were undertaken by the Agricultural Development and Advisory Service (ADAS) (see Allan et al. 2000 in section 8.1.1.2).

8.1.1.2 Field trials of deterrent techniques

In three opportunisitic experiments, Lloyd (1976a) investigated the efficacy of flashing lights. First, following the killing of two 3-4 week old poults, two lights were set-up on a rearing field and their location moved each day. There was no evidence of owls visiting the pens until the fifth night when an owl was observed within 20m of a light. Second, in a similar arrangement no further killing of poults or evidence of owl visits over a 17-day period after a light was set-up. Third, two flashing lights were set-up at a pen in which 11 birds had been killed over 5 days; their positions changed every two to three days. There were no further kills. Lloyd (1976a) undertook further limited experiments in which “glitterbang” (foil strips) bird scarers were suspended within pens. First, a sparrowhawk that had been hunting in a release pen (prior to stocking) ceased its activity for several weeks following erection of “glitterbangs”. No poults were killed in this pen. Second, at another pen where three birds had been killed, no further kills occurred following suspension of these bird scarers. Third, a young sparrowhawk ceased frequenting a pen after a large piece of foil was suspended. Lloyd (1976a) also reported experiments in Europe that had shown large silvered balls were effective in protecting reared game and chickens from diurnal raptors, particularly sparrowhawks and goshawks (Mansfield 1954 and Pfeiffer & Keil 1963 reported in Lloyd 1976a). Allan et al. (2000) conducted an experiment across two gamebird estates that evaluated the effectiveness of three deterrents: (i) hanging bags – c.20 feed/fertiliser bags suspended within feed rides and other areas considered susceptible to predatory birds, (ii) lights and mirrors – 6 flashing roadside lamps each paired with a mirror suspended within feed rides and other areas considered susceptible to predatory birds, and (iii) Mylar tape – positioned around the perimeter of pens at pen height and at c.5m intervals across pens. Suspended bags and mirrors/lights are traditional methods used by gamekeepers, whilst the use of Mylar tape is a more novel technique in this environment. On each of the two estates, one pen was assigned to each of the three treatments and a fourth pen assigned as a control (i.e. no treatment). The effectiveness of the deterrents was assessed by comparing predation levels between the pens via twice-daily searches and examination of carcasses. Once the effects of foliage density and pen age were accounted for, predation levels were lower in all three categories of deterrent pens in comparison to control pens (poults lost per day: hanging bags = 0.48, lights and mirrors = 0.41, Mylar tape = 0.23, control = 1.83. Due to variation in recording by gamekeepers at different pens, however, the authors considered that the results should be treated as provisional. Following on from these results, Allan et al. (2000) examined the cost-effectiveness of the three deterrents relative to a mean 5% loss of poults per pen (1000 birds per pen). From the


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trials of deterrents the rate of poult loss under each treatment was: control = 1 poult/day; Mylar tape = 0.13; lights = 0.22; hanging bags = 0.26. Assuming a 45% return of the estimated ‘saved’ birds the gross income from applying the deterrents was £348, £312 and £296 respectively. In comparison the cost of deploying the deterrents was £35, £88 and £0 respectively. Therefore, the use of all three deterrents provided a cost-effective means of minimising raptor predation. Allan (2001) repeated the earlier field-experiment (Allan et al. 2000) assessing the effectiveness of three deterrents: hangers, lights/mirrors and Mylar tape. The approach differed from the earlier trial in that data was collected solely by a dedicated field-team, rather than relying on data recorded by gamekeepers. The treatments were deployed in the following manner: (i) empty feed bags (c.20 bags/0.25ha) were suspended from a wire at a height of c.1.5-2m inside and along the perimeter of pens. The bags were held flat by the insertion of a stick at the suspended end, whilst the lowest end was cut into a series of vertical strips, (ii) flashing roadside lamps each paired with a mirror (c.40cm x 40cm) were suspended at a height of c.1.5-2m, especially at the edges of pens at c.8 pairs/0.25ha, and (iii) Red and silver Mylar tape (30mm wide) was positioned around the perimeter of pens and across the pens at c.5m intervals at pen height. On each of two estates, each deterrent was applied to a single pen and a fourth pen left unprotected as a control. Data on pheasant mortality was collected by searching for carcasses on a twice-daily basis, from the time of release until the time the pens were first opened. Searches covered the inside of pens and an area extending 25m outside the pen. Key field signs were used to assign each carcass to a category of mortality: avian predation, mammalian predation, unknown predation and unpredated. The principal findings were: (i) Total losses (inside and outside the pen) as a percentage of birds release varied between

pens and ranged from 2% to 8%. Losses to avian predators ranged from <1% to 5%. (ii) The majority of carcasses were found inside the pen (76% and 88% respectively). (iii) Pooling data from pens, causes other than predation (disease, starvation, etc) produced

the biggest single greatest loss inside pens (48% and 46% of losses per estate respectively).

(iv) Avian predation was the second greatest cause of death inside pens (31% and 40% respectively).

(v) Several lines of evidence suggest that sparrowhawks were the most frequent avian predator.

(vi) On most pens the rate of predation during active periods of predation equated to c.1 poult per day.

(vii) There was no significant statistical difference in predation rate by raptors between any of the treatments. This was a consequence of the high degree of variation in the bag treatment between the two estates – highest predation rate in on one estate and lowest rate on the other estate.

(viii) Relative to control pens, the rate of predation on mylar pens was 45% and 73% lower. Due to low sample sizes, Allan (2001) recommended that further trials should be undertaken.

8.1.1.3 Diversionary feeding

In Ireland, Lloyd (1976a) reported the use of dead pigeons to prevent sparrowhawk predation on pheasant poults at a release pen. After four pheasants had been killed, pigeon carcasses were put-out for four days, with the sparrowhawks taking the pigeons but no more pheasants.


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Three days after the last pigeon was provisioned another poult was taken. Provisioning of pigeons was resumed and no further poults were taken even after the supply of pigeons ceased. Harradine et al.’s (1997) questionnaire survey of gamekeepers reported ‘…some measure of success…’ when using diversionary feeding in combination with scarers and pen protection. Estimates from graphical data presented in the report indicated that a total of 26 gamekeepers used ‘Alt. feeding’ for sparrowhawk (n=3), buzzard (n=22) or tawny owl (n=1) with 69% reporting at least partial effectiveness (i.e. successful or partially successful). In Scotland, following recommendations for its implementation by Science and Advice for Scottish Agriculture (SASA) a small number of gamekeepers have reported that diversionary feeding had been effective in reducing buzzard predation at pheasant release pens (SASA, pers comm). In one case, the gamekeeper initiated diversionary feeding in the vicinity of the pen, presenting a carcass (the recommendation was on top of a post) and gradually moved the provisioned food further away. The diversionary feeding was reportedly accompanied by a decrease in losses of poults within the pen. Diversionary feeding was recommended by the findings of the EU’s REGHAB project. This EU project aimed to create the first step to reach long-term, sustainable solutions to reconcile gamebird hunting and biodiversity conservation across Europe.

8.1.1.4 Lethal control A number of predator removal experiments have investigated the relationship between predator density and factors associated with gamebird abundance and productivity (e.g. the GWCT’s Salisbury Plain Predation Control Experiment). Generally, predator removal experiments have focussed on groups of species, which may include all ‘predators’ (which can comprise both avian and mammal predators), or smaller groupings, such as ‘corvids’. In these studies, therefore, the effect of any individual predator species could not be separated from that of other predators. No such predator removal experiments have been undertaken for raptors or ravens, either targeted at specific areas or individual birds. In addition, no licensed lethal control of raptors, for the purposes of protecting livestock, is undertaken in the UK. It is not possible, therefore, to evaluate the potential effectiveness of the lethal control of raptors to reduce impacts at gamebird release pens or outdoor poultry units.

8.1.2 Measures targeted at the habitat or environment

The most effective methods to protect pheasant release pens were reported to be habitat manipulation and game management (for the latter see ‘Measure applied to gamebirds’ below) rather than deterrent devices (Lloyd 1976a; Harradine et al. 1997). Lloyd (1976a) found that the only deterrent specifically aimed at birds of prey was the use of strings criss-crossed over the top of the pen, sometimes threaded with reflectors (e.g. milk bottle tops). On several estates netting was put right over the pen. On others birds were released into a small covered pen within the release pen to acclimatise them. Harradine et al. (1997) reported that the use of measures to protect release pens, providing more cover (and providing decoy food and putting chicks/poults out later than normal) followed a long way


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behind the use of scaring devices. Although not frequently used, protecting release pens physically, particularly with overhead netting, were reported as relatively more successful. Harradine et al. (1997) reported that pen protection (i.e. using overhead netting, wires, tapes and fishing line) appeared to offer a means of excluding raptors from release pens. Data presented in the report indicated that ‘fishing line’, ‘netpen’, ‘netting’, ‘tape’ or ‘wire’ was used by 19 gamekeepers and was considered to be successful in 58% of cases and partly successful in 21% (i.e. at least partly successful in 79% cases). When including the unspecified action ‘protect pens’ (n=17) to those above (36 gamekeepers in total) 61% considered the measure successful and 22% partly successful (i.e. at least partly successful in 83% of cases). Pen protection, however, was reported to have limited application due to the cost and practicality associated with the size of the pens, and the requirement to allow pheasants to leave the pen via the top as they mature. In terms of habitat preferences, pheasants have been shown to prefer shrubby areas. Winter pheasant density within-site was positively influenced by the presence of a high proportion of shrubby cover (100-200cm) (Robertson et al. 1993a) and breeding density within-site was related to the availability of woodland edges with high levels of shrubby cover (30-200cm) (Robertson et al. 1993b). A number of studies have reported lower predation rates in pens with good vegetative cover. Lloyd (1976a) found that release pens with >20% shrub were predated less than pens with <20% cover, pens with at least 60% herb cover were predated half as much as pens with more open herb layers and that pens without either shrub or herb layer were very susceptible to predation. Allan (2001) found that predation was highest in pens that were older and with lower tree foliage density. Kenward (2001) noted that buzzards tended not to kill pheasants when there was above-average shrub, below average deciduous canopy and relatively few pheasants present in the pen. A number of recent effective uses of habitat manipulation have been reported in Scotland, involving methods inside release pens, at feed stations and in the open environment (pers comm. SASA). Inside release pens cover has been provided in the form of brash piles presented both in ‘natural’ piles of cut conifers and in the form of ‘wigwam’ or tented structures. At feed stations cover has been provided with camouflage netting. This approach involved encouraging birds to feed underneath a series of structures that increased incrementally in their complexity and hence degree of protection provided. Finally, cover has been provided in the form of artificial structures within open fields. ‘Hides’ constructed from wooden pallets and straw were provided as refuges, or bolt-holes, for pheasants crossing a field between two woodlands. Prior to the provision of the refuges buzzards had been successfully picking-off birds as they crossed the open field. Also reported from Scotland is the use of a release pen in which one half was fully enclosed with a mesh roof (SASA pers comm). Poults were herded/encouraged into the enclosed section for the night and out again into the open-section in the morning. Although it was not possible to manage every individual poult in this way, a significant proportion of the stock spent the nights in the fully-predator proof enclosure. The application of this technique, however, would be limited by its practicality relative to the scale of the rearing operation.


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8.1.3 Measures applied to game birds

Factors that have been shown to be associated with the rate of predation are poult age, timing of release and size of the release. POULT AGE: Lloyd (1976a) found that almost two thirds (65%) of kills occurred when poults were between 6 and 9 weeks of age. Accounting for the relative availability of different age groups to birds of prey, poults were killed more than expected up to the age of 8 weeks and less than expected after they were 12 weeks old. Sparrowhawks were reported killing poults up to 12 weeks old and buzzards up to 14 weeks old. The proportion of releases suffering predation declined with age at release, from 68% of releases of poults ≤5 weeks of age to only 20% for releases of poults aged >8weeks of age. Lloyd (1976a) considered in addition to larger, older birds being less vulnerable to predators than younger, smaller birds, that age-associated changes in roosting behaviour may also have an effect. Young pheasants begin to roost at about 8 weeks of age (Gill 1973 cited in Lloyd 1976a). As they get older poults prefer to roost dispersed in cover rather than ‘jug’ (roost on the ground) in large packs in the open. From these findings Lloyd (1976a) recommended that poults be released at 7 or, preferably 8 weeks of age. In another study, Allan (2000) found, during field trials of avian deterrents, that in two out of three experimental pens raptor predation was greatest during the first two or three weeks following release of poults. TIMING OF RELEASE: Lloyd (1976a) found that releases in June and July had twice the predation rate of release in August and September. The recommendation was that, if only one release was planned then older birds should be released in August. If two releases were planned then the first batch should comprise birds older than traditionally released, and the second, later batch poults of the standard 6-7 weeks of age. Turner (2007) also found that survival to the start of the shooting season increased with delayed release dates. In terms of survival, delaying the release of birds until late August-early September was suggested as the optimum releasing strategy. SIZE OF RELEASE: Lloyd (1976) found that the proportion of releases predated increased with the size of the release. Releases over 500 birds were predated more frequently than smaller releases. However, amongst large releases (>500 birds) the frequency of predation increased with high stocking density. Allan et al. (2000) examined the economic impact of losses of pheasant poults and the cost-effectiveness of mitigation measures through supplementary stocking. For the majority of pens Allan et al. (2000) estimated that losses to raptors was ≤1% of released birds, equating to 10 birds in a pen holding the median stock of 1,000 poults (see section 7.2.1). The mean cost of rearing an estate-hatched poult to 6-8 weeks of age (release age) was £1.50-£1.80, whilst the mean cost of quality, healthy bought-in 6-8 week old poults was £2.20-£2.50. Therefore, the cost of supplementing a pen with sufficient birds to compensate for losses to raptor predation was in the region of £15-£18 (estate-reared) or £22-25 (bought-in) per pen. The estates in the study released on average around 9,000 birds. Thus, on an average estate the costs of compensating for anticipated losses would be £135-£162 (estate-reared) or £198-£225 (bought-in). The economic value of a pheasant, however, is driven by the sale of the actual shooting with one day’s shooting equating to a cost then of around £20 per bird shot. Using Tapper’s (1992) estimated likely return of released pheasants of around 40% (Turner & Sage 2003 provide a more recent figure of 37.5%), a return of four of the ‘supplementary’


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birds would equate to £80 per pen. For average losses, therefore, resultant income (£720 for the estate) exceeded that of the additional costs of rearing supplementary birds. Extrapolating these calculations up to the occasional higher rates of loss experienced at some pens, the supplementary income would still exceed the additional rearing costs. However, a number of difficulties arise. Compensating for potentially unexpectedly high losses is problematic as their occurrence and magnitude cannot be predicted with any certainty (Allen et al. 2000). Raising significant numbers of supplementary birds raises issue such as capital outlay and over-stocking. STOCKING DENSITY: A number of studies have indicated that the stocking densities of pheasant poults in release pens have exceeded recommended levels, sometimes far in excess. Lloyd (1976a) reported that (based on the length of the perimeter of the release pen) ‘...the Game Conservancy’s recommendations were to allow a yard per bird in releases up to 500 birds and half a yard for larger releases’... In both small and large releases, however, Lloyd (1976a) found that approximately two-thirds of releases were made in pens smaller than recommended. In large groups the frequency of predation increased with high density. It was considered that the effect of density may be due to the birds having inadequate cover to all escape into, and possibly to the actual destruction of the ground cover by the birds themselves (Lloyd 1976a). Allan (2001) reported stocking density for two estates (four study pens on each estate) of 2,570-3,500 poults per ha and 3,750-4,000 poults per ha respectively. The Game Conservancy and Wildlife Trust report a 1988 study of 43 release pens in southern England in which the average stocking density was 2,250 pheasants per ha (Sage et al. 2005). The same reference also cites unpublished data from a more recent (2004) study that showed a mean stocking density of 1,800 birds per ha for a sample of 53 pens from the same areas. More recently, The Game Conservancy Trust (2006ab) and The Code of Good Shooting Practice (2008) recommended that: ‘These provide a rule of thumb, advising that in order to avoid damage to habitat in most situations

shoots should avoid releasing more than 1,000 pheasants per hectare of pen, and more than 700 per

hectare of pen in ancient, semi-natural woodland and that pheasant release pens should not, in total,

take up more than about one third of the woodland area on the shoot.’

‘Where shoots exceed the recommended densities they should be able to demonstrate that their

particular circumstances and management regime (for example, by limiting the period of time birds

are in release pens) does not significantly damage woodland flora and fauna.’

8.1.4 Current practical guidelines for pheasant release pens

Lloyd (1976a) made a number of recommendations for reducing losses to raptors (particularly tawny owls): - AGE OF POULTS: release of older poults of at least 7 weeks old. - VEGETATION: high levels of vegetative cover within the pen with at least 20% shrub cover

and 60% cover of herbs and brambles.


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- SIZE OF RELEASES: where possible release birds in groups of <500. - TIMING OF RELEASES: where possible release birds later in the season. - DESIGN OF PENS: pens should be better constructed to be better proofed against mammalian

predators. - SIZE OF WOOD: pens should be sited in woods smaller than 50 acres and not extend outside

the wood. - SCARING DEVICES: although, only effective in the short-term, hanging devices, flashing

lights and bangers were recognised as useful in protecting poults until they became larger and more self reliant in avoiding predators. Deterrents should also be regularly moved and changed. However, whilst deterrents were recommended, there was no experimental evaluation of their relative effectiveness.

The British Association of Shooting and Conservation (BASC) drew together the various strands of information (including Lloyd 1976a) and published practical guidelines for game managers and gamekeepers to alleviate predation by birds of prey at pheasant release pens (http://www.basc.org.uk). The measures recommended in the guidelines are summarised below: RELEASE PENS: - Plant a variety of shrubs to provide dense cover between 1-2m high over at least 20% of

the pen. - Coppicing existing shrubs/trees may also be helpful. - Maintain thick woody ground cover, such as brambles over at least 60%. - The remaining area should be open ground with short grass. - Always ensure that vegetation within the pen provides a mixture of open areas and

patches of cover. REDUCE AVAILABILITY OF PERCHES: - Cover release pen posts with bags or remove prominent branches so that birds of prey

have fewer places to perch. RELEASE EXTRA POULTS: - Many shoots release extra poults to compensate for small losses to birds of prey. RELEASE OLDER BIRDS: - Consideration should be given to releasing poults at 7-8 weeks; the larger size and

increased experience at this age increases their chances of avoiding predation. REFLECTIVE TAPE: - Stretch single-sided reflective tape across feed rides and open areas within pens. The tape

creates flashing effects, as well as acting as a partial physical barrier. SCARING DEVICES: - Scaring devices should be varied and moved frequently. They should be positioned in and

around the pen at the time of release and removed once poults have matured. LEAVE KILLS WITHIN PEN: - Consider leaving some raptor-killed poults within the pens. Raptors often return to

previous kills and in the absence of such kills the raptors may kill fresh birds. PROVIDE ALTERNATIVE FOOD (DIVERSIONARY FEEDING): - Some gamekeepers provide alternative food, in the form of dead rabbits, away from the

release pen. Scottish Natural Heritage (SNH) advice on preventing predation of pheasants and partridges at release pens reiterates BASC guidance of providing shelter and vegetation cover for poults in and around release pens (SNH 2009a). In addition, the use of deterrents, such as Mylar


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tape and diversionary feeding in the form of dead rabbits placed strategically to move raptors away from release pens is also advocated. 8.2 Outdoor poultry units In the UK, the provision of natural woodland cover by the Federation of Woodland Egg Producers (http://www.woodlandeggs.co.uk/default.asp) has become an established practice, with its producers supplying Sainsbury’s; with the eggs commanding a premium. All member farms are: - Planted with trees which cover at least 20% of the range. - The trees are a mixture of fast growing and slower native trees which are indigenous to

the local area. - The trees are planted close to the house to encourage the hens outside to range. In addition to natural vegetation, cover is also traditionally supplied in the form of artificial structures, such as low ‘gazebo-like’ frames constructed from timber and shade-netting. These approaches are consistent with the UK’s Farm Animal Welfare Council (FAWC) advice that where hens are kept extensively and may be free to range it is important to provide some overhead shelter. In the USA, the National Center for Appropriate Technology (NCAT) has provided information on many aspects of raising poultry on pasture, including protection against predators (http://www.thepoultrysite.com/articles/156/sustainable-poultry-production-overview-part-iii). Avian predator controls include the use of overhead netting, portable radios, realistic scarecrows and suspended CDs to flash reflected light at raptors. The use of flashing (e.g. strobe light) or rotating lights (e.g. rotating beacon) at entry points to poultry houses has been advocated for times when doors need to be open (Berry undated). Anti-predator responses are said to vary between different breeds. It has been stated that young Cornish-cross broilers are not known for seeking shelter from raptors, whilst it is considered that other breeds may seek shelter more readily (http://www.thepoultrysite.com/articles/156/sustainable-poultry-production-overview-part-iii ). 8.3 Lambs In Scotland, SNH advice on how to reduce raven predation on lambs, recommends where possible, either housing ewes giving birth, or close shepherding in lambing parks (SNH 2009b). Lambing on the open hill or unattended parks is regarded as more likely to lead to problems. More detailed guidance for the management of raven predation on livestock is provided by Science and Advice for Scottish Agriculture (SASA 2010): - Make the area less attractive to ravens

o remove potential sources of food (afterbirths, fallen stock, dead wild animals) o clean up spilled feed and proof food sources

- Prevent access o keep vulnerable stock indoors or close to human activity o use tapes or wires to deter ravens from small pens or fields


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- Scare and deter o use a wide range of devices and methods o vary methods randomly and unpredictably o reinforce devices with human activity o link lethal shooting (under licence) with other methods of scaring

- Diversionary feeding o food must be provided away from livestock o most successful when used with scaring techniques where livestock kept o food should be placed out early in the morning and raised off the ground o food provided is subject to the Animal By-Products (Scotland) Regulations 2003

- Lethal shooting o licensed shooting must be part of an overall scaring programme o only shoot ravens in the presence of other ravens o ravens will learn to recognise individuals so vary clothing and vehicle used

In Britain, licences to kill or take birds of prey are issued by Natural England, SNH (previously by the Scottish Government) and the Welsh Government. Over recent years there has been an increase in the numbers of applications for licenses to control ravens by lamb, game and poultry interests. In England and Wales the numbers remain relatively low (England: 3 to 5 applications per year between 2001 and 2011 [Natural England unpublished data]) but are far more numerous in Scotland. In Scotland, licenses are issued usually to help reduce predation during the lambing season, and to a lesser extent, predation outwith the lambing season, or to prevent serious damage to foodstuffs for livestock. Evidence of serious damage occurring, or likely to occur, must be provided before consideration will be given to granting a licence. In addition evidence is required for other scaring techniques having been tried and found to be insufficient (http://www.snh.gov.uk/protecting-scotlands-nature/species-licensing/bird-licensing/preventing-damage/). Licences are granted only where there is no other satisfactory solution. The number of licences issued since 2007 are: 2007 = 62 licences, 2008 = 78, 2009 = 121, 2010 (part-year) = 79 (http://archive.scottish.parliament.uk/s3/committees/petitions/petitionsubmissions/sub-10/10-PE1309E.pdf). There is a requirement for all licence-holders to report back to the licensing authority on activities carried out under licence. However there is no robust and formalised mechanism to measure and record the effectiveness of control conducted under individual licences (although a review of key licensing areas is proposed – B. Ross, SNH, pers. comm.). Typically licensees apply for a new licence year-on-year.


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Table 8.1. Management measures to mitigate predation by birds of prey on pheasants in and around release pens (‘effective’? = view of the author/s).

REFERENCE BIRD PREDATORS MAMMAL PREDATORS STUDY MEASURE/VARIABLE EFFECTIVE?

LLOYD 1976A

TAWNY OWL

SPARROWHAWK

BUZZARD

UNIDENTIFIED

QUESTIONNAIRE SURVEY

REPORTED FIELD TRIALS

OPPORTUNISTIC FIELD TRIALS

CORRELATION BETWEEN RELEASE

PEN HABITAT VARIABLES AND

PREDATION

HANGERS, VARIOUS LIGHTS, FLADRY, MIRRORS,

SCARECROWS, BANGERS, STRINGS, NETTING, DOUBLE-

PENNING, DECOY FEEDING

‘GLITTERBANGS’

FLASHING LIGHTS, ‘GLITTERBANGS

POULT AGE

TIMING OF RELEASE

STOCKING DENSITY

VEGETATIVE COVER

SIZE OF WOOD PEN SITED IN

VARIED

PARTIALLY

PARTIALLY

OLDER POULTS

LATER RELEASE (AUG-SEPT CF JULY-AUG)

LOWER DENSITY IN RELEASES. >500 BIRDS

>20% SHRUB COVER; >60% HERB COVER

<50HA

HARRADINE 1997

TAWNY OWL

SPARROWHAWK

BUZZARD

FOX

QUESTIONNAIRE SURVEY



PREDATION

BANGERS, GAS GUNS, ALARMS, HANGERS, MOBILES,

LIGHTS, MIRRORS, RADIOS, OWL DECOYS, SCARECROWS,

HUMAN PRESENCE

INCREASING COVER INSIDE PENS, ROOFING PENS (E.G.

OVERHEAD WIRES), DELAYING POULT RELEASE UNTIL

BIRDS WERE OLDER

VARIED – BUT GENERALLY NOT VERY EFFECTIVE

VARIED – GENERALLY MORE EFFECTIVE THAN SCARERS

ALLAN ET AL. 2000 BUZZARDS UNIDENTIFIED

FIELD TRIALS



PREDATION

HANGERS

LIGHTS & MIRRORS

MYLAR TAPE

AGE OF PEN

VEGETATIVE COVER (ABOVE 1.5M)

PARTIALLY

PARTIALLY

PARTIALLY

YOUNGER PENS

HIGHER COVER

ALLAN 2001

TAWNY OWL

SPARROWHAWK

BUZZARD

UNIDENTIFIED FIELD TRIAL

HANGERS

LIGHTS & MIRRORS

MYLAR TAPE

VARIED

MARGINAL

YES

KENWARD 2001

BUZZARDS

TAWNY OWLS

SPARROWHAWKS

CORVIDS

FOX



PREDATION

SHRUB COVER

TREE CANOPY COVER (PERCH AVAILABILITY)

STOCK DENSITY

HIGH SHRUB COVER

LOW CANOPY COVER

HIGH DENSITY


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9. Comparison of management techniques The different management techniques described in the review were compared using a scheme based on the Risk Management Options Module of the UK Invasive Non-Native Species Risk Management Scheme. This module compares selected attributes of different management measures, including effectiveness, cost, acceptability, availability and safety by rating and ranking the attributes using a series of five-point scales (Table 9.1). For each attribute of a management measure, a low score indicates a ‘positive’ rating of that attribute that might facilitate use of the measure, whilst conversely a high score indicates a ‘negative’ rating of the attribute that might mitigate against adoption of that management measure (Table 9.2). The Risk Management Options Module does not recommend a specific management measure; rather it provides key information needed to inform decision-making. The scheme allows the comparison of different attributes both within and between management measures. For example, the use of a specific measure may be facilitated by relatively low costs and high availability but constrained by low acceptability from stakeholders or the public. Conversely, a measure that may rate relatively high in terms of acceptability might be constrained by high costs. Between measures, different techniques may have equivalent costs and availability but score differently in terms of, say, environmental impact or stakeholder acceptability. The ranking of the attributes was based on the present author’s interpretation of information extracted from the various sources and expert judgement. This comparative scoring was undertaken for preliminary illustrative purposes only and cannot replace a detailed mathematical synthesis of a similar ranking exercise undertaken by all relevant stakeholder groups (see section 10.3). Table 9.1. Scoring system for the analysis of management options.

Attribute Scoring scale

What are the anticipated direct costs of the

chosen management action?

very low = 0, low = 1, medium = 2

high = 3, very high = 4

How available is the management option? Very available = 0, available = 1, moderately available = 2,

unavailable = 3, very unavailable = 4

What is the anticipated environmental

impact of the chosen action?

zero/minimal = 0, minor = 1, moderate = 2, major = 3, massive

= 4

How acceptable is the action likely to be to

producers?

no/very little opposition = 0, minor opposition = 1, moderate

opposition = 2, major opposition = 3, massive opposition = 4

How acceptable is the action likely to be to

conservationists?

no/very little opposition = 0, minor opposition = 1, moderate

opposition = 2, major opposition = 3, massive opposition = 4

How high a risk does the management

option pose to human safety?

very low = 0, low = 1, medium = 2

high = 3, very high = 4

What is the likelihood that the measures

will be unsuccessful?

very unlikely = 0, unlikely = 1, moderately likely = 2, likely = 3,

very likely = 4

How difficult would it be implement the

management option?

Very easily = 0, easily = 1, with some difficulty = 2, difficult = 3,

very difficult = 4

How long will this management option take

(to see an affect)?

<one week = 0, <one month = 1, < six months = 2, <one year =

3, >one year = 4

What is the likelihood of compliance

problems?

very unlikely = 0, unlikely = 1, moderately likely = 2, likely = 3,

very likely = 4


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Table 9.2 Comparison of management measures.

Ma

na

ge

me

nt

Op

tio

n

Co

st (

dir

ect

)

(ve

ry l

ow

= 0

)

Av

ail

ab

ilit

y

(ve

ry a

va

ila

ble

= 0

)

En

vir

on

me

nta

l Im

pa

ct

(min

ima

l =

0)

Pro

du

cers

Acc

ep

tan

ce

(min

. o

pp

osi

tio

n =

0)

Co

nse

rva

tio

nis

ts a

cce

pta

nce

(min

. o

pp

osi

tio

n =

0)

Ris

k t

o H

um

an

Sa

fety

(ve

ry s

afe

= 0

)

Lik

eli

ho

od

th

at

un

succ

ess

ful

(ve

ry u

nli

ke

ly =

0)

Dif

ficu

lty

of

ap

pli

cati

on

(v

ery

ea

sy =

0)

Tim

e n

ee

de

d f

or

succ

ess

(da

ys

= 0

)

Lik

eli

ho

od

of

com

pli

an

ce

pro

ble

ms

(v

ery

un

lik

ely

= 0

)

Visual and auditory deterrents 1 1 1 2 0 0 2 1 0 0

Translocation 3 2 1 1 2 1 2 3 1 2

Lethal control 2 1 1 0 4 1 2 2 0 3

Conditioned taste aversion 4 3 1 3 1 1 2 4 1 3

Exclusion 3 1 2 3 1 0 1 2 0 0

Habitat modification - pens 1 1 1 1 0 0 1 1 0 0

Livestock management 2 1 1 3 0 0 1 2 0 0

Diversionary feeding 1 1 1 2 0 0 1 1 0 1

Compensation scheme 3 4 0 0 2 0 3 3 3 3

Incentive scheme 3 4 1 3 1 0 3 3 3 3

Scores for each attribute range from 0 to 4 with a low score indicating a ‘positive’ rating of the attribute and a high score a ‘negative’ rating.


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10. Discussion 10.1 Extent and magnitude of impacts Pheasant release pens Generally, losses of pheasant poults in and around release pens to raptor predation are low, commonly ≤1% of birds released into pens where predation occurs (Lloyd 1976a; Harradine et al. 1997; Allen et al. 2000). Typically the fox has been implicated as the main predator with most predation occurring once poults have begun initial movements out of the release pen. Losses to raptors represent a small percentage of losses relative to total losses to all causes of mortality (predation, disease, weather, cannibalism). Before the start of the shooting season typically 25% of birds released are lost to all causes (e.g. Turner & Sage 2003). The impacts of raptors, however, are not distributed evenly across all shoots. Although the vast majority of shoots do not suffer significant losses, a small number do suffer high losses, estimated at >5% at one in 30 (3.3%) shoots (Lloyd 1976a) and >10% at ‘...some...’ shoots (Harradine et al. 1997). Since these reports were produced there have been significant increases in buzzard numbers. Losses to raptors can often be overestimated compared to other sources of loss. This is influenced by the different behaviour of raptors relative to other predators (Lloyd 1976a; Allan et al. 2000). Raptor activity, particularly diurnal species such as buzzard and sparrowhawk, in and around release pens is very noticeable. The subsequent discovery of killed poults can often be attributed to the observed raptor. Allan et al. (2000) found no significant relationship between the estimated avian predation levels and the frequency of raptor occurrence as recorded by gamekeepers at release pens. In contrast, mammalian predators are generally active at night and may be more likely to remove killed birds. There are few studies that have examined rates of loss at sites claiming high rates of raptor predation, there is a need for independent, quantitative assessments of the scale of raptor predation at sites claiming such rates of loss Evidence is not available to determine whether individual ‘problem’ buzzards can be implicated in predation events. A study has shown that only a minority of buzzards frequent release pens but the data did not permit the investigation of links between buzzard presence and predation records (Kenward et al. 2001a). A number of factors have been identified that are associated with the level of predation at pheasant release pens: POULT AGE - predation declined as the age of poults at release increased; TIMING OF RELEASE - predation was twice as frequent among poults released in June-July than among those released in August-September; SIZE OF RELEASE: predation increased with the size of the release group; POULT DENSITY: density had no effect on avian predation in releases of <500 birds but in larger releases high densities increased predation; VEGETATION - predation was lower in release pens with >20% shrub cover and pens with at least 60% herb cover; SIZE OF WOOD - predation was higher in woods >50 acres. From previous studies it was concluded that for the great majority of shoots far more pheasants were lost to other predators, disease, accidents and starvation in the period after


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release, than the 1-2% losses to birds of prey in the release pen (Lloyd 1976a, BASC undated). It was recommended that efforts to minimise these losses would have much the greater benefit. In terms of indirect losses to raptors, the information required in order to make an assessment of the extent and magnitude of any effects of raptor activity (outwith direct predation) on poult health and well-being are not available. It is not known how any predator-induced stress compares to the baseline stress imposed on reared animals by numerous factors, such as stocking levels (recommended and over-stocking) and competition for resources, such as food, water, warmth and cover. Lloyd (1976a) found no evidence for a significant effect of raptor activity on poult behaviour, whilst Allan et al. (2000) found no relationship between losses of poults and the extent of raptor activity at pens. The appropriate physiological studies, however, to investigate the relationship between acute stress events (e.g. predator activity) and chronic baseline stress and their relative and/or additive effects on physiology, health and mortality have not been undertaken. It should be noted, however, that the most recent studies on levels of impact were completed over at least ten years ago (e.g. Kenward 2001a), and in some cases 35 years ago (e.g. Lloyd 1976a). Over the ensuing period the populations of common birds of prey have undergone various changes in numbers and range. In the case of buzzard increase in population size and range is ongoing. Investigations of the extent and magnitude of the impacts of birds of prey at release pens have not been undertaken in the context of the current status of raptor populations. Outdoor poultry units The only known European study to have empirically investigated the extent and magnitude of raptor predation at outdoor poultry units was undertaken in Bresse, France (Stahl et al. 2002). Overall, 70% of farmers lost poultry to predation (all predators). The overall loss to predators was estimated as 6.3% of all chickens and the range of losses per flock were 0-34%. Predatory birds (rapors, corvids, gulls) were responsible for 24% of all kills, with raptors responsible for 10% (goshawk 0.6%, buzzard 0.4%, unknown 9%). The economic cost of avian attacks by all predatory birds, by all raptors and by buzzards alone corresponded to 29 Euros/ha, 12 Euros/ha and around 5 Euros/ha respectively. The majority of all chickens killed (68%) was due to mammalian predators, with the 19% of known fox kills equivalent to 23 Euros/ha. The findings contrasted with perceptions held by poultry farmers that losses to predators in general and to birds of prey specifically were greater. The results of an earlier survey in Bresse, showed that farmers believed that overall losses to predation were higher (12%) and that avian predators had a major impact on poultry (estimated losses to raptors and corvids as 40% and 23% respectively). Similar to the gamebird industry, a tendency to over-estimation of losses to avian predators was considered to be due to their being more likely to attack during the day, perching in the area, rarely removing prey from the site and eating prey in situ. In the UK there has been no known similar investigation with available reports on raptor predation (principally sparrowhawk and buzzard) limited to ‘backyard’ poultry flocks.


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As for gamebirds, in terms of the indirect effects of raptors, the information required in order to make an assessment of the extent and magnitude of any effects of raptor activity (outwith direct predation) on poultry health and productivity are not available. No information was found that empirically tested the extent and magnitude of any causative role of birds of prey in any indirect losses arising from their presence at outdoor poultry units, e.g. relationship between smothering events or egg production and raptor activity. Likewise, the appropriate physiological studies to investigate the relationship between acute stress events (predator activity) and chronic baseline stress and their relative and/or additive effects on physiology, health and mortality have not been undertaken. Sheep and lambs Studies that have investigated the impact of predation by birds of prey on lambs have generally found that losses were minor relative to total losses to all causes (e.g. white-tailed eagles: Marquiss et al. 2003ab, Simms et al. 2010). For example, on Mull, Scotland, most white-tailed eagles scavenged lambs that had died from other causes and/or took very few live lambs. In some cases, however, a small number of individual pairs took higher numbers of lambs (Marquiss et al. 2003ab). Evidence indicated that many of the lambs killed were not viable. Studies have concluded that mitigation measures would be most effectively targeted by implementing measures to reduce overall lamb mortality (e.g. improvement of ewe nutrition), rather than target measures against white-tailed eagles (Marquiss et al. 2003a). The increased productivity would more than offset losses to predation. In recent years, a new conflict has developed between sheep farmers and birds of prey that involve flocks of non-breeding ravens. There are no known UK studies that have attempted to quantify the extent and magnitude of this impact. An increasing conflict between ravens and grazing sheep and cattle arose in Germany during the 1990s, with reports ranging from injuries to individual young animals to large-scale losses; accompanied by sensationalist media reports (Brehme et al. undated). Detailed scientific investigation, however, showed that impacts were essentially limited to weakened animals whose long-term viability was compromised prior to the intervention of ravens. 10.2 Mitigation measures The literature review revealed that a wide-range of avian management techniques have been used in attempts to alleviate predation by raptors and other birds of prey on livestock around the world; many of these techniques have also been applied at gamebird release pens. Very few of the documents, however, included empirical data relating to evaluation of the effectiveness of these techniques. Rather, ‘evidence’ for their efficacy, or not, was generally descriptive and anecdotal. The few experimental trials that have been undertaken (e.g. Lloyd 1976a, Allan et al. 2000, Allan 2001) have been limited in their robustness being either opportunistic one-off trials, having few replicates or confounded by other factors, including variation in recording effort between treatment sites. Due to this lack of empirical data it was not possible to undertake any analysis of the evidence for the effectiveness of any technique, or to compare the degree of effectiveness between different techniques. Consequently, evaluation of the applicability of the various management techniques for protecting pheasants at release pens, outdoor poultry units and lambs relied on the interpretation of the conclusions of the various authors of the literature reviewed and the opinion of the authors of the present report and experts consulted during its production.


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10.2.1 Visual and auditory deterrents

Visual and auditory scaring techniques have been deployed frequently against raptors in numerous situations; with varying degrees of deterrence and duration of their effectiveness being reported. In the UK, gamekeepers have deployed a wide-range of different types of visual and auditory (primarily visual) deterrents in and around pheasant release pens, (Lloyd 1976a, Harradine et al. 1997; Allan et al. 2000). A questionnaire survey of game managers affected by raptors, concluded that the effectiveness of the various deterrents was reported to be varied, but in general were considered to be relatively ineffective (Harradine et al. 1997). As discussed in section 9.1.1, however, this overall conclusion appears to be a pessimistic interpretation of the data presented in the report. For example, of those gamekeepers deploying ‘scarers’ against buzzards, 51% reported success or partial success. No information is provided in the report on the mode of use of deterrents in terms of the degree of proactive deployment. It is not known to what extent guidelines (see below) to maximise effectiveness are followed. Two field-experiments have been conducted on visual deterrents (hanging bags, lights/mirrors and Mylar tape) at release pens and have provided some support for a degree of effectiveness (Allan et al. 2000; Allan 2001). In the first experiment, all three deterrents appeared to reduce levels of predation by raptors (Allan et al. 2000). In the second, predation rates at two Mylar tape pens was reduced by 45% and 73% compared to predation rates at control pens (Allan 2001). As a number of factors contributed to reducing the robustness of these two field-experiments further field-trials were recommended. Most animals will exhibit fear or wariness towards any novel object placed in their environment and will avoid it. Dispersal can also be induced through a startle reflex as a result of the sudden presentation of visual or auditory stimuli. Virtually all visual and auditory deterrents, used on their own, will gradually become less effective due to habituation (a process by which animals come to realise that the deterrent does not actually present a real threat and gradually ignore the stimulus). Thus, for all visual and auditory deterrents any initial effectiveness will inevitably decline. To maximise effectiveness, through prolonging the process of habituation, deterrents should: (i) be as realistic as possible, (ii) be temporally and spatially unpredictable, (iii) present as real a threat as possible, (iv) be presented as infrequently as possible, and (v) be reinforced or replaced with alternative type/s of devices or techniques (see section 10.2.8 Integrated Management Strategy). To achieve this, effigies and scarecrows, for example, should be constructed to be physically lifelike and animated, moved frequently between different locations, interchanged with alternative models, and reinforced with other stimuli. Essentially, the more biologically meaningful a deterrent is the greater the period of habituation. For some categories of livestock, deterrents may only need to resist habituation for a relatively short, but critical period, such as during the pheasant poult maturation or lambing periods. Another important factor in maximising effectiveness is to instigate deterrent measures as soon as the bird of prey species of concern commences utilising a site, i.e. before a pattern of attendance is established. Once a pattern is established, the birds will be more difficult to deter. In deploying deterrent techniques, the degree to which gamekeepers and other livestock managers adhere to these guidelines is not known. The more proactive and dynamic the deployment of deterrents the greater the probability of success.


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The effectiveness of deterrents has yet to be comprehensively tested in field experiments.

10.2.2 Diversionary feeding

Diversionary feeding has been reported to have had some success in reducing predation at pheasant pens for sparrowhawk (Lloyd 1976a) and buzzard (Harradine 1997). For example, data in Harradine et al.’s (1997) questionnaire survey of gamekeepers reported that of 22 gamekeepers deploying alternative feeding against buzzards 68% reported success or partial success. More recently, reduction of buzzard predation through diversionary feeding has been considered to have been effective at a small number of release pens in Scotland (see section 9.1.1.3). In one case in Scotland for example, diversionary feeding was initiated in response to predation at the release pen, i.e. deployed reactively (see section 9.1.3). Diversionary feeding, however, could also be used proactively (i.e. prior to predation) in situations where predation is expected to occur. If predation has been occurring seasonally, diversionary feeding can be instigated just prior to the release of poults into the release pen. Carrion of naturally occurring local prey species (e.g. woodpigeon or rabbit) should be provisioned at an appropriate location away from the pen. The food should be provisioned off the ground (e.g. fencing post) to avoid mammal predators and at regular intervals until the poults (or other stock) have matured sufficiently to minimise their vulnerability to predation. Diversionary feeding should only be undertaken during this relatively short period of vulnerability. Against the background of promising examples of the use of diversionary feeding, in Scotland there is an ongoing initiative for cooperation between SNH and the National Park Authority to develop and deliver within the National Park a training scheme for gamekeepers in the application of diversionary feeding (SNH, pers. comm.). The nature and scope of the proposed course have yet to be formalised but will be based around the experiences of estates where the approach has proved effective. A number of potential concerns are associated with diversionary feeding, such as increasing juvenile survival (and hence population size), the risk of attracting additional birds of prey into the area, legal issues with the provision of carcasses and the provision of carcasses containing lead shot. All of these concerns, however, can be addressed with careful consideration of the approach to deploying the technique (Natural England draft guidance). Diversionary feeding only needs to be deployed for the relatively short period of time that poults are maturing within pens, with the food targeted at the individual birds that are active within the vicinity of the pen. During this period juvenile buzzards are dependent on their parents and so are unlikely to garner any significant additional benefits from diversionary food over and above that which would be provided by parents anyway from natural prey abundant at this time of year. The period of diversionary feeding is also relatively short. Carcasses that are supplied can be whole, freshly shot specimens of naturally occurring prey, such as rabbits, woodpigeons or corvids; killed using non-lead shot. Also, carcasses should be supplied off the ground and unconsumed carcasses removed. At pheasant release pens, diversionary feeding has historically been conducted in individual case-by-case circumstances and has not been investigated using controlled, replicated field


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trials. Such trials would elucidate the degree of effectiveness and factors affecting its level of success, including for example the mode of presentation of diversionary food and the age-component of the raptor population susceptible to the treatment.

10.2.3 Bird of prey removal

10.2.3.1 Translocation

Translocation of raptors in order to ameliorate wildlife conflict has largely proved to be ineffective in the long-term for one reason or another: birds can return to their former range, other birds can take their place and cause similar conflict, suitable areas for translocation are lacking, or the problem is simply moved elsewhere (Linnell et al. 1997; Cade 2000; Fischer and Lindenmeyer 2000). Further issues with translocation involve the potential for detrimental impacts on the welfare of the relocated individuals (Massei et al. 2010). Despite the general consensus on the long-term ineffectiveness of the translocation of raptors to reduce conflict, there are examples of more positive outcomes, notably concerning goshawks in Sweden. Here, translocation of birds showed that few returned after being moved more than 30km (Marcstrom & Kenward 1981). It was concluded that transporting goshawks for release more than 30km away was a viable alternative to killing them in order to reduce hawk numbers at a site. These translocations, however, took place in autumn and winter, a period during which juveniles (representing over 80% of birds captured) would be dispersing. A more novel potential approach to ‘relocating’ ‘problem’ individual raptors would be to capture and temporarily house the birds until pheasant poults had matured and fully dispersed from the release pens; releasing the raptors back at the original site. Such an approach would be akin to the temporary retention of wounded raptors taken in by animal sanctuaries and released following recuperation. Permanent removal by housing, for example in an aviculture collection, represents another option. These approaches to relocation/removal would require reconciliation of associated ethical and legal requirements. For buzzards in the UK there are a number of factors that may potentially influence an effective outcome of translocation. Increase in their numbers and expansion of their range (Clements 2000, 2002), together with the density and distribution of shoots, will limit opportunities for suitable release sites. Buzzards also exhibit strong natal philopatry, either remaining in their natal area during their first winter or returning towards their natal area in the spring (Walls and Kenward 1995). It is likely, therefore, that translocated buzzards will exhibit a propensity to return to their natal area. It is not known to what extent this may occur, the period of time to return or extent of variation between individual birds. Similarly, the extent of occurrence and variation in the timing of other buzzards replacing removed individuals is not known. Post-fledging, young buzzards are dependent on their parents for a period of 6-8 weeks (Cramp 1980). With most egg-laying occurring in mid to late-April (Austin and Houston 1997), an incubation period of 36-38 days and fledging period of 50-55 days (Cramp 1980), this period of dependency coincides with the period when pheasant poults are in release pens. There could be welfare considerations, therefore, in separating juvenile buzzards from parents during this period. Monitoring the health of removed birds would be feasible during the temporary housing and release of birds back into their home range but not in the case of immediate translocation to another location.


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In sparrowhawks, the young disperse when they become independent of parental care in late July or August, by which time they have been out of the nest for 3-4 weeks (Newton 1975; Newton and Marquiss 1983). The dependent period, therefore, coincides with the initial poult maturation period. In Scotland translocation of sparrowhawks has shown that birds can return or are replaced by others at the site of capture (Humphrey et al. 2010; Newton and Marquis 1991). The aim of this latter study was to explore the effectiveness of translocation (and a second technique - Mylar tape) for reducing the frequency of sparrowhawk attacks on racing pigeons in the immediate vicinity of the loft. In the end it was not possible to draw conclusions on effectiveness due to insufficient sample sizes (lofts), issues over experimental design and the limited amounts of observational data collected at lofts. The experimental design was criticised for having weak statistical power to detect any effect of treatment due to small sample size allied to attacks and kills by sparrowhawks at lofts being very rare events (Amar and Wilson undated). Any future field trials aiming to examine the effect of raptor translocation in reducing attacks on pheasant pens would need to deal with similar issues concerning experimental design. Although translocation of raptors to mitigate wildlife-conflicts has been considered to be largely ineffective, the context in which translocation is deployed is a key consideration. For translocation to be effective a number of conditions need to be met: (i) it is recognized as providing a short-term solution, (ii) that the birds removed are ‘problem’ individuals, specializing in the prey item, (iii) that their potential replacements are less keyed into the prey than those individuals removed, (iv) that the removed birds do not return, and (v) that the impacts of raptor predation at the release pen are significantly reduced. The issue of buzzard predation at release pens could meet many of these conditions. The pheasant poult rearing period is of relatively short duration but information on the other criteria is lacking. Kenward et al. (2001a) showed that only a minority of buzzards frequented release pens. No studies are known that provide information on return rates of translocated buzzards, replacement periods for alternative individuals, or the occurrence of ‘problem’ individuals specializing in predation of poults. Another factor that might predispose the effective translocation or removal of specific buzzards is that the minority of buzzards shown to frequent release pen were fledged from nests closer than average to the pens (Kenward et al. 2001a). The consequences of the removal or prevention of nesting within a defined distance from pens is unknown. As stated above however, the presence of individual buzzards at pens has not been linked to directly to records of predation.

10.2.3.2 Lethal control

Under the Wildlife and Countryside Act (1981), licences can be issued to take a small number of birds of prey for the purpose of preventing serious damage. There has been a small but increasing number of applications for licenses to kill buzzards made to Natural England by gamebird and poultry interests - six applications in 2011 compared to three applications during the previous 8 year period 2003-2010 (NE data). To date there have been no licenses granted in respect to buzzards or any other raptor, for this purpose, in England, neither in Wales and Scotland. For ravens, however, a number of licenses are issued annually, principally in Scotland. Following issue, the licence-holder is required to submit a returns form detailing the numbers of birds taken. There is no formal process, however, for


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evaluating the efficacy of the licensed control in terms of mitigating the impacts of the predation. Licensed control is most associated with the control of ravens with respect to sheep and lambs, almost exclusively in Scotland. Licences issued to protect livestock ranged between 62 and 121 per year between 2007 and 2009. Many successful applicants apply for renewal of the licence year-on-year. The current licensing strategy in Scotland, serves to provide stakeholders with a means of reinforcing non-lethal deterrent techniques, at an intensity that currently does not provide concern in respect to the ravens’ overall conservation status. This strategy is consistent with the licensing authorities need to balance the safeguarding of populations of formerly declining (often through persecution) predatory species, whilst also addressing the concerns of stakeholders (R. Hastings, Scottish Government, pers comm). SNH are proposing to review key areas of licensing, and this is likely to include licences to control birds for preventing serious damage (to livestock, fisheries etc.) (B. Ross, SNH, pers comm). The review would include an examination of exactly what licences are expected to achieve and the evidence-base upon which licensing decisions of this kind are made. An evaluation of the efficacy of lethal control would require a controlled, replicated field study in which the numbers and activity of ravens and levels of predation is compared between treatment and control sites before and after application of lethal control. Such an experiment could be incorporated into the framework of licensed control, through detailed independent monitoring at sites pre- and post-shooting. Attitudes of gamekeepers vary considerably in their views and response to raptor predation. It has been argued that where raptor predation represents insignificant losses to the shoot, lethal control is unnecessary. However, in circumstances where impacts are significant and ecological techniques are not effective then it has been argued that consideration should be given to more intrusive techniques, such as the elimination of particular problem individuals (Vinuela and Arroyo 2002). As is the case for translocation however, the ecological consequences (replacement rate) of such removal are unknown, and so consequently its potential effectiveness cannot be predicted. Lethal control can also be applied to predators (avian and mammalian) other than birds of prey and would have both specific and general benefits with respect to predation of livestock. Large raptors can prey on gulls and corvids; flocks of which are attracted to livestock holdings. In a recent study in Scotland, corvids were the highest avian constituent of buzzard diet, representing 14% of all prey remains at nest sites (Swan 2011). Reducing the presence and numbers of gulls and corvids through control practices will lessen the attractiveness of holdings to raptors. On a broader-scale, the reduction of gulls and corvids will reduce the overall incidents of predation. Control could be achieved through a combination of non-lethal visual and auditory deterrence, exclusion and appropriately licensed lethal trapping and shooting. With respect to the control of predators other than raptors, the EU Concerted Action Reconciling Gamebird Hunting and Biodiversity (REGHAB) project considered that ‘...little attention has been paid to the indirect potential positive effect that some raptors may have on game populations by preying on, for example, corvids, or displacing other raptor species’ (Vinuela and Arroyo 2002).


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10.2.4 Conditioned taste aversion

The potential for applying Conditioned Taste Aversion (CTA) to resolving conflict between raptors and various stakeholder interests has been recognised (Cowan et al. 2000). CTA has been successfully induced in a number of raptor and other avian predator species. Presently, however, development of applications of the technique in the field has been limited, due to equivocal results and differences of opinion amongst wildlife researchers. The GWCT concluded, as a result of field trials, that it was highly unlikely that CTA could ever be made to work in the case of foxes and gamebirds (GCT 1999). Despite long-lasting CTA having been induced in captive foxes the application of the technique in wild foxes posed a number of obstacles (e.g. accuracy of dosage due to variation in fox size and some foxes never visiting bait stations) that where considered too expensive (financially and manpower-wise) to warrant further development. Similar issues are associated with the use of CTA against raptors (Allan et al. 2000). Raptors, for example, may differ in body size between species (e.g. buzzard/sparrowhawk) and within species (male/female sparrowhawk), posing issues with dosage. Another potential issue is with the turn-over of individuals, such as dispersing juveniles. The use of CTA against raptors, however, would appear to be less problematic than against foxes. At pheasant release pens CTA could be targeted at identified individual birds; in some cases facilitated by the individual returning to a recent kill. In the UK, CTA has been induced in captive peregrine falcons and was considered to have shown some promise in the field, with resident peregrines appearing to be deterred from taking racing pigeons (Musgrove 1996; A. Musgrove reported in JNCC 2000). It remains the case, however, that research would be required on the effect of appropriate agents on raptors and development of a suitable mode of delivery in the wild. The wide-scale use of a CTA agent would require licensing of a novel product, with significant costs in time and finance.

10.2.5 Exclusion techniques

Exclusion techniques (nets and closely spaced wires) are generally evaluated as a very effective bird management technique. Effectiveness depends on the degree to which birds are excluded (e.g. closer spacing between wires); the closer that wires are installed the more they approximate to a net. Properly installed and maintained netting will provide complete protection for a resource and is often recommended as the only technique that is consistently effective in preventing bird damage. The greater the degree of exclusion, however, the more expensive the technique is. For this reason netting tends to be restricted to high value resources. Netting and lines have been traditionally used to protect crops and fish stocks. Their use against raptors is largely untested and the practicality and cost of installation to protect general livestock unknown. It remains an option, however, to install overhead netting or wires above paddocks/pens that are of a manageable area. Such overhead wiring has been successfully and economically installed over commercial fishponds to deter cormorant predation; farming activities were able to take place unhindered beneath the wires. At pheasant release pens, both total exclusion techniques and barrier techniques have been deployed. Total exclusion methods have included overhead netting, fishing line, wires and


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tape. In a questionnaire survey of gamekeepers (Harradine et al. 1997) 83% reported such pen protection to be successful or partially successful. Other exclusion methods have used smaller netted enclosures within the larger release pens into which poults are initially released and release pens divided into separate enclosed and open sections. These latter techniques may mitigate, in some circumstances, the concerns that roofing pens interferes with the requirement to allow pheasants to leave the pen via the top as they mature. Barrier methods have involved the suspension of Mylar tape (a potential visual deterrent in addition to a physical barrier) across identified raptor flightlines to interfere with attacks on poults. In the case of the latter, it is essential that sections of tape are regularly varied in their location to minimise the opportunity for raptors to acclimatise to their configuration and adjust their approach flight accordingly. At pheasant release pens and ourdoor poultry units mammalian predators (principally fox) have been shown to be the main cause of losses to predation. Irrespective of proofing against birds of prey, improvements in proofing pens against mammalian predators would be beneficial as recommended by previous studies (Lloyd 1976a).

10.2.6 Habitat manipulation

Habitat management could involve a range of measures including the provision of adequate natural and artificial cover, manipulation of perch availability and the removal of right-angled corners in pens. At release pens, of the principal factors identified in reducing raptor predation is the presence of sufficient cover both within and around the pens. Recommendations are for at least 20% shrub cover and at least 60% herb cover (including brambles) (Lloyd 1976a, 1976b). Adequate suitable cover is essential to allow birds to develop their natural ant-predator behaviour when jugging (sleeping on the ground) and roosting (sleeping in trees) and also provides protection by screening and/or physically protecting the birds. It is not known, however, to what extent gamekeepers adhere to the recommend levels of cover, or indeed other guidance. Studies have shown that it is not uncommon for release pens to be stocked above recommended levels. Over-stocking may have detrimental consequences for the retention of sufficient vegetative cover. The GCT, for example, recognised that ‘...the release of large numbers of pheasants into a pen over a long period can lead to changes in the ground flora in some instances up to 15m around the pen...’ (Game Conservancy Trust 2003; Sage et al. 2005). Creative solutions in the provision of cover have been effectively implemented in individual cases. These have included the provision of brash piles or structured brash wigwams within release pens, and timber or ‘tented’ ‘refuges’ in the wider habitat outside of pens, to protect pheasants during transit in open habitat or at feed stations. For poultry, the provision of woodland cover has become an established practice (Woodland Egg Scheme). However, there is a delay in the principal benefits of the technique being realised. This is due to the few intervening years that are required for the ‘whips’ (i.e. young trees approx. 100cm-180cm) that are planted to mature. One of the principal reasons for the planting of whips, as opposed to more mature trees is the economics of scale, associated with the large numbers of trees required for a typical poultry paddock. Although an accepted management option, the provision of permanent woodland cover is not suitable for all poultry


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premises, as in some holdings the poultry houses are moved to new pasture between years. Poultry premises also provide artificial cover in the form of timber frames fitted with overhead shade netting. Again, the extent of cover provided is subject to economies of scale. The provision of additional temporary and/or permanent structures would benefit poultry units during the period of tree maturation, or substitute for trees, in holdings with permanent or temporary placement of poultry houses, respectively. Although the degree of cover advocated for game bird release pens is impractical for poultry pens, the provision of a significant degree of cover could be achieved. Initially cover could be provided in the form of artificial shelters whilst more long-term cover in the form of trees and shrubs is being planted and established. Interference to maintenance and husbandry practices within the pens could be minimised by planting the trees and shrubs in parallel lines, as in commercial orchards. Provision of cover has a sound ecological basis. The domestic chicken is primarily descended from the red junglefowl (Gallus gallus) that typically lives in areas with a mix of open ground and dense vegetation. For domestic poultry, in addition to providing protection from direct predation attempts, artificial and natural cover would provide a refuge for poultry that may feel threatened by raptors flying low overhead. The provision of refuge areas would facilitate a reduced likelihood of stress and panic in the flock, which in turn would reduce the likelihood of potential smothering events. Reduced stress is, also, likely to be reflected in improved condition, growth and egg production rates. A simple technique to minimise the potential for smothering or crowding events involves the removal of right-angled corners in pens and has been advocated in the poultry industry in the USA. Pheasant pens would also benefit from such an approach.

10.2.7 Measures applied to livestock

A recurring management theme in the review of mitigation measures for raptor-livestock conflict was changing livestock practices to reduce the exposure of vulnerable animals to predation. Such changes have included either moving animals indoors to give birth, or relocating them to areas of the holding away from areas of raptor activity and closer to human activities. Breeding livestock earlier so that young attain a larger size earlier and are thus less vulnerable to predation (Shivik 2004) has limited application. The timing of breeding livestock is constrained by biological limits, environmental conditions and marketing conditions. For sheep, close shepherding during the lambing period and/or the relocation of stock have been advocated. Moberly et al. (2003) identified indoor lambing as an important preventive measure against fox predation in Britain. It was recognised, however, that housing was costly and impractical for some sheep-management systems. In circumstances where indoor housing has been unavailable, lambing has taken place in temporary structures, such as poly-tunnels; one technique advocated to protect lambs from white-tailed eagles in Scotland (SNH 2004, 2006). Extra shepherding would only be required for the eight week period over which lambing takes place, but would require skilled shepherds. In the USA, ‘shepherding’ through the use of guardian animals appears to be relatively widespread. Dogs, donkeys and llamas have been used to protect a range of livestock (predominantly sheep) against primarily mammalian predators. There is little information on


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their use of guardian animals against raptors. Of two cases in the USA, dogs failed to reduce predation by eagles on sheep, but small flocks of geese successfully deterred predation by hawks on poultry. The most effective shepherds are human. For sheep, close shepherding during the lambing period and the routine removal of dead stock have been frequently advocated. Studies have shown that lambs from multiple birth litters were more susceptible to predation by foxes (White et al. 2000) and boar (Choquenot 1997). This is due to the ewe’s greater problems in maintaining vigilance compared to ewes with single lambs and also to the lambs being smaller than single-born lambs (Nash et al. 1996; Simm et al. 1996). The same issue of maintaining vigilance will also be a critical factor with respect to other predators, including ravens and raptors. Advocated in the literature is the retention of young animals indoors until they have attained a size and weight that makes them less vulnerable to predation. In the UK, however, livestock owners have a number of concerns with retaining animals indoors. In the poultry industry, preventing birds from accessing outdoor paddocks is not considered an option - ad-lib access to outdoor habitat is fundamental to their husbandry (Schofield 2009). More intensive husbandry may also require additional labour costs that are prohibitive. Similarly, denying ewes and lambs access to grazing increases the need for supplementary rations, whilst keeping animals penned together for long periods can increase stress and disease transmission (Shivik 2004, Schofield 2009). An over-arching concern with indoor husbandry is that it is contrary to the government and consumer desire for more extensive outdoor rearing practices. For pheasants, the size of pens and the stocking density of poults are factors that may influence survival rates. The use of large pens minimises mass kills by mammalian predators, feather picking, and the build up of disease and impact on ground flora (Carroll & Robertson 1997). As stated previously a number of studies have reported stocking densities far in excess of recommended levels, which has the potential to impact detrimentally on the quality of the vegetative cover. Releasing older poults and undertaking releases later in the season are associated with lower levels of raptor predation. Addressing the issue of later releases, however, is not necessarily straightforward. For example, on estates which hatch or rear their own chicks, the longer that chicks are kept in small cages on the rearing field, the greater is the chance of feather and pecking and the chance of disease (Lloyd 1976a). Many shoots like to rear twice or three times to maximize use of their rearing equipment (Lloyd 1976a). Late releases also involve having small birds when the weather may be getting cooler and wetter. Finally, birds put out late in the season don’t have much time to get acclimatised and fully feathered, so the quality of the birds is reduced in the early part of the season. In poultry, anti-predator responses are said to vary between different breeds. In the USA, for example, it has been stated that young Cornish-cross broilers are not known for seeking shelter from raptors, whilst breeds other than Cornish cross may seek shelter more readily (http://www.thepoultrysite.com/articles/156/sustainable-poultry-production-overview-part-iii). In gamebirds inappropriate anti-predator behaviour has been identified as a factor in increasing vulnerability to predation (Leif 1994; Dowell 1990 cited in Parish and Sotherton 2007). In one study in Scotland, for example, reared grey partridge suffered significantly


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higher predation rates than wild birds (Parish et al. 2007 or Parish and Sotherton 2007). High post-release predation rates in grey partridge have been shown to be related reduced vigilance behaviour and maladaptive habitat use (Ratanen et al. 2010a,b).

10.2.8 Integrated management strategy

Mitigation of the effects of predation is an ongoing process in which a pro-active and integrated management strategy (IMS) is necessary. An effective IMS will not only supplement and interchange different techniques from the same category of management measure (e.g. visual and auditory scaring techniques) but will also integrate different categories of measures, such as scaring, habitat manipulation and decoy feeding. In Australia, the integrated use of combinations of scaring devices is advocated to reduce the predation of wedge-tailed eagles on lambs (DEC 2007b). In the USA, it is recognised that no single method is 100% effective and that an integrated management program that includes both preventive and selective control methods provides the best protection (Franklin and Powell 1994). In the UK, combinations of visual and auditory scaring techniques, habitat modification and decoy feeding are used as an integrated management strategy to alleviate raptor predation at pheasant rearing pens. Practical guidelines have been published by BASC and have been reiterated by SNH. However, the extent and depth to which guidelines are followed and the degree of pro-active management (as opposed to reactive) is not known. The effectiveness of any bird deterrent will depend on a number of factors in addition to the deterrent itself or the IMS, such as the motivational state of the animal and the availability of alternative resources. Motivational state will be influenced by the degree of hunger and availability of alternative resources. In a review of human-wildlife conflicts, prey availability was commonly identified as an important factor determining levels of conflict; low abundance of natural prey was associated with higher predation on livestock/game species (Matchett and O’Gara 1987; O’Gara and Rightmire 1987; Graham et al. 2005). Optimal Foraging Theory predicts that birds select feeding sites so that food intake is ‘optimised’ (Krebs and Cowie 1976). In circumstances with a very attractive, cost-effective prey source, in order to reduce or prevent predation a level of deterrence is required that reduces the raptor’s net energy gain, prompting the bird to switch to alternative, more profitable prey. This will be more easily achieved if alternative natural prey is available locally.

10.2.9 Economical management strategies

In order to derive cost-effective management strategies knowledge about the relative costs of losses to predation and of deploying mitigation measures is necessary. The most recent field studies (Kenward 2001a) to have provided estimates of raptor predation were undertaken ten years ago, since when the UK buzzard population has continued to increase in numbers and range. Up-to-date estimates of the extent and magnitude of impacts are required. A major limitation revealed by the literature review is the lack of empirical data supporting the advocacy by authors of various management techniques. The only known experimental trials on deterrents at pheasant release pens provided some evidence for effectiveness in reducing predation rates but due to small sample sizes and confounding factors the results were considered to be preliminary (Allan et al. 2000, Allan 2001). Based on estimated predation rates, pertaining at the time, it was estimated that the deterrents were cost-effective to deploy in response to average levels of predation. Supplementary stocking was also estimated to be cost-effective under the same level of predation. As for estimates of raptor


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predation, up-to-date investigations of the efficacy and cost-effectiveness of mitigation measures are required.

10.2.10 Compensation and incentive schemes

Direct compensation schemes pay owners an amount for actual losses incurred. An indirect or incentive payment scheme rewards producers for undertaking actions that tolerate predator presence whilst concurrently reducing the opportunities for conflict to occur. Compensation schemes have essentially been developed for extensive low-intensity livestock rearing, as opposed to high-intensity rearing as practised in the gamebird and poultry industries. In extensive systems, compensation schemes are potentially viable options. For intensive systems, however, quantifying losses is more difficult, due to the numbers of stock involved and the complexity of ways in which stock productivity, development and welfare could be affected; in addition to direct predation. In such systems it would be very difficult to be able to prove that losses were being incurred due to predators, especially indirect losses. Clear guidelines would need to be established regarding the instigation of compensatory payments. Further disadvantages of compensation are the potentially prolonged procedure required to compile and submit claims and uncertainty over the level and duration over which payments would be made available. There would be significant difficulties in respect to validation and ‘trigger’ points for payments. An affected factor of productivity would have to be shown to have fallen below the lower limit of its ‘normal’ range for the specific stock premises in question. Also, the presence of an avian predator, for example, in the ‘vicinity’ of a holding, would not constitute ‘proof’ that the bird, rather than an alternative event in the same time-scale, was the instigator of the reduced productivity. In comparison to direct compensation, incentive schemes offer a number of benefits, for example, schemes promote a positive value on the presence of predators, in contrast to the perception of them as a ‘problem’ that is engendered by direct compensation. In addition, the positive management activities that incentive payments facilitate reduce the likelihood of detrimental interactions between predators and livestock and/or increase productivity that would offset losses if any predation did occur. In contrast, direct compensation may offer no incentive to adopt alternative practices that would help alleviate conflict. In the present conflict areas under consideration the relevant predators (buzzard, sparrowhawk and raven) are not considered to be of conservation concern. 10.3 Consensus building A recent introduction into the debate on the raptor-gamebird conflict is the application of a Consensus Building Approach (Redpath et al. 2004). Consensus Building Approaches have been used frequently in resolving a variety of conflicts, such as sustainable use of natural resource (e.g. land and water) management (e.g. Warner 2000). These approaches involve a wide variety of techniques but essentially involve mediated face-to-face meetings of the various stakeholder groups in order to achieve a resolution of their differences. Such an approach using hierarchial decision trees and multicriteria decision analysis has been applied to the hen harrier-red grouse conflict in the UK (Redpath et al. 2004). The process evaluated the perspectives of two groups of stakeholders, grouse managers and conservationists, and their acceptability of different management solutions to the conflict. Although the two groups ranked different criteria and management options more highly,


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overall the process was regarded as a valuable tool in moving the debate forward. The process developed dialogue between the groups and highlighted areas for compromise and common-ground, e.g. a high value was placed on diversionary feeding by both groups. It was considered that an important aspect of the decision-modelling approach was that working within the neutral framework of mathematical models, as opposed to a typically more adversarial framework, reduced personal animosity and distrust. Despite this, however, there was a belief amongst participants that despite the potential agreement about best options for reducing conflicts, a lack of trust between the two groups would prevent implementation (Redpath et al. 2004). Stakeholders concluded that more dialogue and understanding between the groups was required and that objective research was required to test the effectiveness of some of the management options. 10.4 European perspective (REGHAB Project) In most European regions, gamebird hunting is an important socio-economic activity in rural areas. Hunting may also be potentially beneficial to biodiversity, by promoting conservation and management of habitats within a strategy of "conservation through wise use of natural resources". However, in some cases there may be conflicts between hunting and the conservation of biodiversity, which appears when hunting is non-sustainable and intensive and, particularly, when predators are subjected to illegal killing with the purpose of maximising game numbers. Predators (including raptors) are perceived within a large part of the hunting sector as an important limiting factor for small game populations, and thus as an enemy of hunters; in some cases leading to illegal control of protected species. As a result of such illegal activities, the protectionist movement sometimes perceives hunting as a detrimental activity for conservation. The EU Concerted Action the REGHAB project aimed to create the first step to reach long-term, sustainable solutions to reconcile gamebird hunting and biodiversity conservation across Europe.

The project involved members of the scientific community from five countries (France, Spain, Portugal, UK, Finland), and also representatives of Spanish hunting organisations, and small and medium-sized enterprises (ERENA, Portugal and APROCA-CLM, Spain). Other stakeholders (other hunting representatives, conservation NGOs and government agencies) were invited to participate in the workshops organised throughout the project, in an attempt to compile contrasting information, and discuss the polarised views of the problem.

In terms of impacts, as a general rule, it was uncertain that raptors caused substantial losses to hunting bags and when compared to other factors (e.g. changes in habitat quality) raptor predation may be a relatively minor factor in limiting gamebird populations. In certain circumstances, however, it was also concluded that raptors can cause a significant decrease in the number of birds available for shooting in the autumn or limit some gamebird populations.

In terms of management measures, the project covered the same techniques, with similar conflicting opinions about practicality and effectiveness, as detailed in the preceding sections of the present report (Arroyo 2002; Kenward 2002). As in the UK there was a paucity of empirical studies on management techniques. One conclusion from the project in respect of predation and predator control was that:

‘Research on the efficacy of different methods to limit predation on gamebirds is very limited.

• It is thus necessary to develop new methods and test existing ones to decrease predation in

hunting systems.’ (Vinuela and Arroyo 2002).


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11. Conclusions and Recommendations Although birds of prey can cause predation problems for game, poultry and sheep/lambs, the extent of the problem appears to be limited, with potentially serious impacts manifest only at a local scale. Guidance on a number of management measures are available to mitigate the local impacts of predation but their effectiveness remains unclear and it is uncertain to what extent guidance is followed. It should be noted, however, that the most recent scientific studies that have estimated the extent and magnitude of impacts and the effectiveness of mitigation measures were conducted over a decade ago and longer. Since that time the UK population of buzzards has increased in numbers and range and for ravens there have been regional increases. This lack of contemporary data is one of a number of gaps in knowledge within the wildlife-conflict areas under consideration. To address the numerous gaps in knowledge a number of studies and field trials are recommended that would be beneficial to increase understanding of the interactions between birds of prey and game/livestock and to the formulation of future policy in these areas. 11.1 Pheasant release pens On average, losses to raptor predation at pheasant release pens were low representing ≤1% of released birds, equivalent to around 5% of the losses to all known causes (i.e. all predators, disease, chilling etc). A small number of pens, however, experienced higher levels of raptor predation of >10%; and there were some unsubstantiated reports of levels in excess of this. Typically the major cause of predation was mammals, principally the fox with most predation occurring once poults have begun initial movements out of the release pen. A number of factors have been shown to be related to the level of predation at pheasant release pens: POULT AGE, TIMING OF RELEASE, SIZE OF RELEASE, POULT DENSITY, VEGETATION, AND SIZE OF WOOD. Empirical evidence for indirect effects (e.g. smothering, stress-related mortality) of bird of prey activity on pheasant poults is lacking. A variety of methods have been used in attempts to prevent or reduce predation by raptors at pheasant release pens: SCARERS, EXCLUSION, HABITAT MANIPULATION AND DIVERSIONARY

FEEDING. Information on factors affecting predation has previously been synthesised into guidance for the management of release pens. The level of implementation of this guidance is not known. The gamebird industry has reported that deterrents (scarers) are generally ineffective. This, however, contrasts with survey returns reporting individual gamekeepers experiences. The limited field trials that have been undertaken have also indicated some level of effectiveness.


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There is a paucity of field trials that have evaluated the effectiveness of techniques to mitigate raptor predation at release pens, including deterrents, exclusion, habitat manipulation and diversionary feeding. A lack of scientific evidence that specific techniques are effective does not reflect a measured lack of efficacy but the fact that the necessary controlled, replicated field experiments have not been performed. Field studies Quantification of losses The most recent studies that have attempted to quantify the impact of raptor predation at pheasant release pens were undertaken over a decade ago and focused on the average situation rather than estates claiming particularly high losses. Since then, in addition to the buzzard population having increased in numbers and range, the prevalence of large numbers of non-breeders in the population (Kenward et al. 2000) and the implications for predation has become better understood. Contemporary studies are required that place estimates of predation in the context of current populations of raptors and other predators. Empirical evidence for an indirect effect of raptors on pheasant pens, either behaviourally (e.g. smothering events) or physiologically (e.g. increased stress-related mortality) are lacking. Studies are recommended that: - Quantify the extent and magnitude of losses of poults at pheasant release pens to

raptors (in particular buzzards) in the context of losses to all causes. Focus these studies on the small number of estates that are claiming high levels of loss.

Where buzzard predation is occurring, quantification of losses is necessary in order to assess whether the activity imposes a significant cost to game managers. Quantification of predation losses is also necessary in order to evaluate the cost-effectiveness of approaches to mitigating the impacts. Field studies should undertake a detailed evaluation of the magnitude of direct impacts on pheasant release pens using a combination of techniques – e.g. monitoring and analysing kills at release pens, tracking buzzard activity relative to pens and monitoring prey delivered to nests. For the latter technique, recent advances in digital technology have improved the capability and cost-effectiveness of evaluating the composition of raptor prey delivered to nests. - Evaluate the potential for indirect effects of raptors on the behaviour and physiology of

pheasant poults and implications for mortality rates. The investigation of indirect impacts would involve both captive experiments (large open-air pens) and field studies. In a captive environment stress parameters can be monitored relative to events (presentation of a predator/model) that are directly controlled by the experimenters. Mitigation measures There is a paucity of empirical studies that have investigated the efficacy of measures to mitigate the impacts of raptors at pheasant release pens. Those that have been conducted


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have suffered from constraints such as small sample size and the continuity and consistency of data collection. As average predation rates are very low, any future field trials will require a robust experimental design to ensure a sufficiently large sample to achieve adequate statistical power. Studies are recommended that: - Evaluate the effectiveness of the most promising scaring techniques (e.g. reflective

tape).

- Evaluate the effectiveness of the most promising exclusion methods (e.g. partial roofing with net or wires; fully proofed sections within the release pen).

- Evaluate the effectiveness of the most promising habitat management techniques (e.g.

natural and artificial cover).

- Evaluate the effectiveness of diversionary feeding.

- Evaluate methods for the removal of individual raptors, the ecological consequences and the effectiveness in reducing predation. This study would address the criteria in 10.2.3.1.

- Undertake a survey of release pens to evaluate the level of compliance with existing

recommendations for managing raptor problems at release pens.

- Compare the features of pens or estates claiming to experience high levels of raptor loss with those not experiencing such problems.

Ideally field trials of mitigation measures should be carried out on a series of shooting estates with different treatments assigned to matched release pens replicated across all estates. For the experiment to have sufficient statistical power the study would need to focus on release pens that are subject to predation levels at the higher end of the scale of impacts. The implementation of meaningful field trials will rely on a high and consistent degree of cooperation from the pheasant rearing industry. 11.2 Outdoor poultry units In France, an empirical study revealed that losses to raptors were relatively low in contradiction of farmers’ perceptions of raptors imposing a major impact. Mammalian predators (principally foxes) had the largest impact. No similar studies are known that have investigated the extent and magnitude of bird of prey impacts on outdoor poultry units in the UK. Empirical evidence for an indirect effect of raptors on poultry units, either behaviourally (e.g. smothering events) or physiologically (e.g. decreased productivity or increased stress-related mortality) are lacking. Quantification of losses Studies are recommended that:


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- Quantify the extent and magnitude of losses of poultry at outdoor units to raptors (in particular buzzards) in the context of losses to all causes.

- Compare the rates of reported problems between different poultry unit types.

- Evaluate the potential for indirect effects of raptors on the behaviour and physiology of poultry and implications for productivity and mortality rates.

Mitigation measures There is a paucity of empirical studies that have investigated the efficacy of measures to mitigate the impacts of raptors at outdoor poultry units. The benefit of undertaking field trials on the effectiveness of mitigation measures would be dependent on the results from an evaluation of the extent and magnitude of impacts above. 11.3 Sheep and lambs Studies that have investigated the impact of predation by birds of prey on sheep and lambs have generally found that losses were minor relative to total losses to all causes. In white-tailed eagles, for example, most individuals scavenged lambs that had died from other causes and/or took very few live lambs. In some cases, however, a small number of individual pairs took higher numbers of lambs. Sheep carrion is an important component of the diet of ravens. Predation by ravens, however, has also been shown to be small and restricted to animals whose survival was anyway in doubt. Deliberate injury was an exception and involved diseased animals or unviable young, but occasionally also in young not protected by their dams. Ravens exploited risk situations leading to peck injuries in young animals and/or dams around birthing. Deaths occurred in animals which were ill or weak anyway. The killing of healthy animals was not observed. General conditions, in terms of livestock management, were considered to play a crucial role in the accumulation of ravens at a lambing park. Guidelines exist for minimising the presence of ravens but the extent and detail to which these recommendations are followed is not known. In the UK in recent years, conflict between sheep farmers and ravens has shifted from territorial pairs of ravens to itinerant flocks of non-breeders. The occurrence of such flocks is consistent with recorded population increases in some regions of the UK. Data on the ecology of these flocks and their interactions with sheep/lambs is lacking. Quantification of losses Studies are recommended that: - Quantify levels of losses of lambs to ravens, focussing on the activity of non-breeding

flocks, in the context of losses to all causes.

- Investigate the status and feeding ecology of non-breeding flocks of ravens. Mitigation measures There is a paucity of empirical studies that have investigated the efficacy of measures to mitigate the impacts of birds of prey, principally ravens, on lambs. Previous studies that have


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found relatively minor losses to raptor predation have concluded that mitigation measures would be most effectively targeted by implementing measures to reduce overall lamb mortality, rather than target measures against the raptor. There is little information on the degree of implementation of guidelines for protecting lambs and their effectiveness. Studies are recommended that: - Investigate factors associated with raven predation on lambs and compare mortality at

farms relative to implementation of recommended guidelines to reduce conflict.


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12. References

Alberta Sheep & Wool Commission. 2007. Alberta Sheep. Predator Control. http://www.absheep.com/documents/PredatorControl.pdf

Allen DS, Packer, JJ, Blanchard C., Feare CJ. 2000. Raptors and the rearing of Pheasants: problems and management needs. ADAS Consulting Ltd. Unpublished report to the British Association for Shooting and Conservation.

Allen DS. 2001. Raptors and the rearing of Pheasants, Part II: A preliminary evaluation of techniques to reduce losses of young pheasants to raptors at release pens. ADAS Consulting Ltd. Unpublished report to the British Association for Shooting and Conservation.

Amar A, Redpath S, Sim I, Buchanan G. 2010. Spatial and temporal associations between recovering populations of common raven Corvus corax and British upland wader populations. Journal of Applied Ecology 47: 253-262.

Amar A, Wilson J. Undated. RSPB Scotland response to the licensed translocation of sparrowhawks. Conservation Science Department, RSPB Scotland. http://www.rspb.org.uk/Images/sparrowhawksand%20pigeonsannex_tcm9-187598.pdf

Andelt WF. 2004. Use of livestock guarding animals to reduce predation on livestock. Sheep & Goat Research Journal 19: 72-75. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1002&context=icwdmsheepgoat

Andelt W, Hopper SN. 2000. Livestock guard dogs reduce predation on domestic sheep in Colorado. Journal of Range Management 53(3): 259-267.

Anon. (undated). Using explosive cartridges (Bird Frite®) to scare black cockatoos from crops. Pp1

Arroyo B, Vinuela J. 2002a. Conclusions from Workshop I. Ciudad Real, 24-25 September 2001. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB).

Arroyo B, Vinuela J. 2002b. Conclusions from Workshop III. Amboise, 30-31 May 2002. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB).

Arroyo B. 2002. Conclusions from Workshop II. Aberdeen, 9-10 February 2002. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB).

Asheim LJ, Eik LO. 2005. Animal welfare conditions for free ranging sheep in Norwegian predator habitats. Biotechnology in Animal Husbandry 21(5-6): 105-109.

Ashmole NP. 1987. Sparrowhawk catching and returning repeatedly to prey. Scottish Birds 14(3): 182.

Austin GE, Houston DC. 1997. The breeding performance of the buzzard Buteo buteo in Argyll, Scotland and a comparison with other areas in Britain. Bird Study 44: 146-154.

Avery MI, Winder FLR. 1990. Roseate Tern in Red Data Birds in Britain (L. A. Batten, C. J. Bibby, P. Clement, G. D. Elliot & R. F. Porter, eds.) pp 208-212. Nature Conservancy Council & RSPB. T & A. D. Poyser, London.

Avery ML, Cummings JL. 2004. Livestock depredations by black vultures and golden eagles. Wildlife Damage Management, Internet Center.


12 June 2012

Avery ML, Pavelka MA, Bergman DL, Decker DG, Knitttle CE, Linz GM. 1995. Aversive conditioning to reduce raven predation on California Least tern eggs. Journal of the Colonial Waterbird Society 18(2): 131-138.

Avery ML, Humphrey JS, Tillman EA, Phares KO, Hatcher JE. 2002. Dispersing vulture roosts from communication towers. USDA, National Wildlife Research Center, Gainesville, Florida, USA.

Baillie SR, Marchant, JH, Leech DI, Joys AC, Noble DG, Barimore C, Grantham MJ, Risely, K, Robinson RA. 2009. Breeding Birds in the Wider Countryside: Their Conservation Status 2008. BTO Research Report No. 516. BTO, Thetford http://www.bto.org/birdtrends.

Baker SJ, Feare CJ, Wilson CJ, Malam DS, Sellars GR. 1993. Prevention of breeding of Canada Geese by coating eggs with liquid paraffin. International Journal of Pest Management 39(2): 246-249.

Barlow GG, Bock K. 1984. Predation of fish in farm dams by cormorants, Phalacrocorax spp., Australian Wildlife Research 11: 559-566.

BASC. 2009. Policy on Raptors. BASC. (undated). Birds of prey at pheasant release pens: a practical guide for game managers

and gamekeepers.

Baxter AT, Bell JC, Allan JR, Fairclough J. 1999. The interspecificity of distress calls. Bird Strike Proceedings.

Baxter A. 2002. Evaluating bird control for the waste management industry. Journal of Wastes Management, February 2002.

Baxter A, Bone S, Pringle H, Eassom A, Dennis N. 2007. Appendix 2: CSL Wild birds as Vectors for the spread of AIV from poultry units in: Network Simualtions of Disease Transmission in the Poultry Industry in GB. Defra Project SE4206.

Bell DV, Austin LW. 1985. The game-fishing season and its effect on overwintering wildfowl. Biological Conservation 33: 65-80.

Beranger J. 2007. Protecting heritage turkeys from predators. http://www.albc-usa.org/downloads.html#turkey

Berry JG. (undated). Wild Bird Control in the Poultry House. Oklahoma Cooperative Extension Service ANSI-8209.

Bishop J, McKay H, Parrott D, Allan J. 2003. Review of international research literature regarding the effectiveness of auditory bird scaring techniques and potential alternatives. Unpublished report to Defra.

Bodey TW, McDonald R, Bearhop S. 2011. Mesopredators constrain a top predator: competitive release of ravens after culling crows. Biology Letters 5: 617–620.

Bomford M, O’Brien PH. 1990. Sonic deterrents in animal damage control: a review of device tests and effectiveness. Wildlife Society Bulletin 18: 411-422.

Bomford M, Sinclair R. 2002. Australian research on bird pests: impact, management and future directions. Emu 102(1): 29-45.

Booth TW. 1994. Bird dispersal techniques. Prevention and control of wildlife damage (ed. R.M. Timm), pp19-23. Great Plains Agricultural Council, Wildlife Resources Committee and Nebraska Cooperative Extension Service, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln.

Bourne J. 2001. Prevention of predator damage in poultry flocks. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex916


12 June 2012

Bradley BF, Bernhardt GE, Cepek JD, Dolbeer RA. 2002. Lasers as non-lethal avian repellents: potential applications in the airport industry. Federal Aviation Administration Technology Conference, 10pp.

Brehme A, Wallschlager D, LanggemachT. Undated. Kolkraben und die Freilandhaltung von Weidetieren – Untersuchungen aus dem Land Brandenburg. 19:32.

Bro E, Reitz F, Landry P. 2005. Grey partridge population status in central northern France: spatial variability in density and 1994-2004 trend. Wildlife Biology 11: 287-298.

Brough T. 1968. Recent developments in bird scaring on airfields. The problems of birds as pests (eds. R.K.Murton and E.N. Wright), pp. 29-38. Academic Press, London

Broyer J, Fournier JY, Benmergui M, Varagnat P. 1993. Le grand cormoran en Dombes. Bulletin Mensuel O.N.C. 178, 36-41

Bruggers RL, Brooks JE, Dolbeer RA, Woronecki PP, Pandit RK, Tarimo T, Hoque M. 1986. Responses of pest birds to reflecting tape in agriculture. Wildlife Society Bulletin 14: 161-170.

Burger GV. 1964. Survival of ring-necked pheasants released on a Wisconsin shooting preserve. Journal of Wildlife Management 28:711-721.

Butchko PH. 1990. Predator control for the protection of endangered species in California. Proc. 14th Vertebrate Pest Conference, 237-240. University of California, Davis, California.

Cade TJ. 1986. Reintroduction as a method of conservation. Raptor Res. Rep. 5:72-84. Cade TJ. 2000. Progress in translocation of diurnal raptors. Pp 343-372 In: Chancellor RD

and Meysburg BU (eds) Raptors at Risk. World Working Group on Birds of Prey.

Carroll J, Robertson P. 1997. Integrating pheasant management and woodland conservation. Game Conservancy Ltd, Fordingbridge, Hampshire.

Choquenot D, Lukins B, Curran G. 1997. Assessing lamb predation by feral pigs in Australia’s semi-arid rangelands. Journal of Applied Ecology 34: 1445-1454.

Christens E, Blokpoel H. 1991. Operational spraying of white mineral oil to prevent hatching of gull eggs. Wildlife Society Bulletin 19: 423-430.

Clements R. 2000. Range expansion of the Common Buzzard in Britain. British Birds, 93: 242-248.

Clements R. 2002. The Common Buzzard in Britain: a new population estimate. British Birds 95: 377–383.

Coates PS, Spencer JO, Delehanty DJ. 2007. Efficacy of CPTH-treated egg baits for removing Ravens. Human-Wildlife Conflicts 1(2): 224-234.

Colorado Division of Wildlife (undated). Raptors: owl, eagle, falcon, hawk. B-41-B-44. Conover MR. 1984. Comparative effectiveness of Avitrol, exploders and hawk-kites in

reducing blackbird damage to corn. Journal Wildlife Management 48(1): 109-116.

Conover MR, Dolbeer RA. 1989. Reflecting tapes fail to reduce blackbird damage to ripening cornfields. Wildlife Society Bulletin 17: 441-443.

Cope D, Vickery J, Rowcliffe M. 2005. From conflict to coexistence: a case study of geese and agriculture in Scotland. Pp 176-191 In: Woodroffe R, Thirgood, S and Rabinowitz A (eds) Conservation Biology 9: People and Wildlife. Conflict or Coexistence?. Cambridge University Press.

Cote IM, Sutherland WJ. 1995. The scientific basis for predator control for bird conservation. English Nature Research report No. 144.


12 June 2012

Cotgreave P. 1995. Relative importance of avian groups in the diets of British and Irish predators. Bird Study 42: 246-252.

Cowan DP, Reynolds JC, Gill EL. 2000. Reducing predation through conditioned taste aversion. In Behaviour and conservation, (eds. L.M. Gosling & W.J. Sutherland). Cambridge University Press. Pp 281-299.

Cramp S. 1980. Handbook of the Birds of Europe, the Middle East and North Africa. Volume II. Hawks to bustards. Oxford University Press.

Cramp S, Perrins CM. 1994. Handbook of the Birds of Europe, the Middle East and North Africa. Volume VIII. Crows to Finches. Oxford University Press.

Crooks KR & Soule M. 1999. Mesopredator release and avifaunal extinctions in a fragmented system. Nature, 400: 563-566.

Cross T. 2002. Common Raven (Raven) Corvus corax. In The Migration Atlas: movements of the birds of Britain and Ireland (eds C.V. Wernham, M.P. Toms, J.H. Marchant, J.A. Clark, G.M. Siriwardena & S.R. Baillie), pp 626–628. T. & A.D. Poyser, London.

Dare PJ. 1986. Raven Corvus corax populations in two upland regions of North Wales. Bird Study 33: 179-189.

Davies RAG. 1999. The extent, cost and control of livestock predation by eagles with a case study on black eagles (Aquila verreauxii) in the Karoo. Journal of Raptor Research 33(1)67-72.

Defra 2010. Wildlife Management in England: A policy making framework for resolving human-wildlife conflicts. Department for Environment, Food and Rural Affairs.

http://archive.defra.gov.uk/wildlife-pets/wildlife/management/documents/policy-making-framework.pdf

Defra 2011. Defra wildlife management policy. http://archive.defra.gov.uk/wildlife-pets/wildlife/management/documents/overarch-policy.pdf

Department of Environment and Conservation (DEC). 2007a. Fauna Note No. 3. Netting to reduce bird damage. Department of Environment and Conservation, Western Australia.

Department of Environment and Conservation (DEC). 2007b. Fauna Note No. 17. Wedge-tailed Eagle. Department of Environment and Conservation, Western Australia.

Department of Environment & Heritage (DEH). 2007. Little corella (Cacatua sanguinea) Resource document.

Dimmick CR, Nicolaus LK. 1990. Efficiency of conditioned aversion in reducing depredation by crows. Journal of Applied Ecology 27:200-209.

Draulans D. 1987. The effectiveness of attempts to reduce predation by fish-eating birds: a review. Biological Conservation 41: 219-232.

Driver J. 2006. Raven Corvus corax population census of northwest Wales, 1998 to 2005. Welsh Birds 4: 442–453.

Durdin C. 1993. Little Terns and Kestrels. British Wildlife 4: 194-195.

Endangered Wildlife Trust’s Wildlife Conflict Prevention Group. (undated). A guide to the responsible resolution of raptor conflict on farmland. www.andersonafrica.co.za/.../Raptor_conflict_resolution_on_farmland.pdf

Environment Council, The. 2007. Hen Harrier dialogue: Combined Working Groups. Meeting transcript.


12 June 2012

Erickson WA, Marsh RE, Salmon TP. 1992. High frequency sound devices lack efficacy in repelling birds. Proceedings 15th Vertebrate Pest Conference, pp. 103-104. University of California, Davis.

Fellows DP, Paton PWC. 1988. Behavioural response of cattle egrets to population control measures in Hawaii. Proceedings 13th Vertebrate Pest Conference, pp. 315-318. University of California, Davis.

Fischer J, Lindenmeyer DB. 2000. An assessment of the published results of animal relocations. Biological Conservation 96: 1-11.

Foster TS. 1979. Crop protection with Xironet. Proc. Bird Control Seminar 8: 254-255.

Franklin WL, Powell KJ. 1994. Guard Llamas: a part of integrated sheep protection. Iowa State University Extension Publication. Ames, IA. http://www.extension.iastate.edu/Publications/PM1527.pdf

French L, Parkhurst J. 2001. Managing wildlife damage: Canada goose (Branta canadensis). Virginia Cooperative Extension Publication No. 420-203. http://www.ext.vt.edu/pubs/wildlife/420-203/420-203.html

Fuller-Perrine LD, Tobin ME. 1993. A method for applying and removing bird-exclusion netting in commercial vineyards. Wildlife Society Bulletin 21: 47-51.

Game Conservancy Trust. 1999. Conditioned Taste Aversion – the end of the line. 31:57-60. Game Conservancy Trust, Fordingbridge.

Game Conservancy Trust. 2003. Woodland conservation and pheasants. Game Conservancy Trust, Fordingbridge.

http://www.gwct.org.uk/documents/woodland_conservation_and_pheasants.pdf

Game Conservancy Trust. 2006a. Guidlines for Sustainable gamebird releasing. Game Conservancy Trust, Fordingbridge. http://www.gwct.org.uk/documents/releasing_guidelines_2.pdf

Game Conservancy Trust. 2006b. New Guidelines for Sustainable gamebird releasing. Game Conservancy Trust, Fordingbridge.

http://www.gameshootstandards.co.uk/docs/Releasing_guidelinelr.pdf

Gibbons DW, Amar A, Anderson GQA, Bolton M, Bradbury RB, Eaton MA, Evans AD, Grant MC, Gregory RD, Hilton GM, Hirons GJM, Hughes J, Johnstone I, Newberry P, Preach WJ, Ratcliffe N, Smith KW, Summers RW, Walton P & Wilson JD. 2007. The predation of wild birds in the UK: a review of its conservation impact and management. RSPB Research Report No. 23, RSPB, Sandy.

Gill EL, Whiterow A, Cowan DP. 1999. A comparative assessment of potential conditioned taste aversion agents for vertebrate management. Applied Animal Behaviour Science 67: 229-240.

Glahn JF, Ellis G, Fioranelli P, Dorr BS. 2001. Evaluation of moderate and low-powered lasers for dispersing double-crested cormorants from their night roosts. Proceedings 9th Wildlife Damage Management Conference. Pennsylvania State University, University Park, PA.

Gorenzel WP, Conte FS, Salmon TP. 1994. Bird damage at aquaculture facilities. Prevention and control of wildlife damage, pp. 5-18. Institute of Agriculture and Natural Resources.

Graham K, Beckerman AP, Thirgood, S. 2005. Human-predator-prey conflicts: ecological correlates, prey losses and patterns of management. Biological Conservation 122: 159-171.


12 June 2012

Green JS, Woodruff RA, Tueller TT. 1984. Livestock guarding dogs for predator control: costs, benefits and practicality. Wildlife Society Bulletin 12:44-50.

Green JS, Woodruff RA, Andelt WF. 1994. Do livestock guarding dogs lose their effectiveness over time? Proc. 16th Vert. Pest Conf. 41-44.University of California, Davis, California. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1021&context=vpc16

Harradine J, Reynolds N, Laws T. 1997. Raptors and gamebirds - a survey of game managers affected by raptors. Wrexham, BASC.

Harris RE, Davis RA. 1998. Evaluation of the efficacy of products and techniques for airport bird control. LGL report TA2193 to Aerodrome Safety Branch, Transport Canada.

Hedges LVJ, Olkin I. 1985. Statistical methods for meta-analysis. Academic Press, Orlando, Florida, USA.

Henderson I, Parrott D, Deppe C. 2004. Racing pigeons – impact of raptor predation. Central Science Laboratory (Defra) report to Scottish Natural Heritage.

Hessler E, Tester JR, Siniff DB, Nelson MM. 1970. A biotelemetrical study of survival of pen-reared pheasants released in selected habitats. Journal of Wildlife Management 34:267-274.

Heydon M, Reynolds J. 2000.

Hibler SR. 1999. Defending Whiteman Skies. Flying Safety 55(4): 20-21 Hinsley SA, Redpath S. 1996. Impacts of raptor predation on red grouse, homing pigeons and

songbirds in Britain. Report to JNCC/SOAEFD.

Humphreys EM, CarringtoN-Cotton A, Wernham CV. 2010. A review of an exploratory trial on Sparrowhawk attack rates at pigeon racing lofts in relation to some management practices. BTO Scotland, School of Biological and Environmental Sciences, University of Stirling.

Hygnstrom ES, Craven SR. 2005. Hawks and Owls. Pp E53-E62 In: The Handbook: Prevention and control of wildlife damage. Interent Center for Wildlife Damage Management. http://haywood.ces.ncsu.edu/nreos/wild/pdf/wildlife/HAWKS_N_OWLS.PDF

Inglis IR. 1980. Visual bird scarers: an ethological approach. Bird Problems in Agriculture (eds. E.N. Wright, I.R. Inglis and C.J. Feare), pp 121-143. BCPC Publications, Croydon, England.

Inglis IR, Huson LW, Marshall MB, Neville PA. 1983. The feeding behaviour of starlings (Sturnus vulgaris) in the presence of ‘eyes’. Z. Tierpsychol. 62,181-208.

Ison AJ, Spiegle SJ, Morishita TY. (undated). Predators of Poultry; Ohio State University Extension Fact sheet. http://ohioline.osu.edu/vme-fact/0022.html.

Jarman PJ, McKenzie DC. 1983. Behavioural mitigation of damage by Galahs to a wheat trial. Australian Wildlife Research 10: 201-202.

JNCC 2000. The Report of the UK Raptor Working Group. Stationary Office, London.

Jones 1972. The bird pests of British agriculture in recent centuries. The Agricultural History Review 20: 107-125.

Keller T, Vordermeir T. 1994. AbschluBbericht zum Forschungsvorhaben EinfluB des kormorans (Phalacrocorax carbo sinensis) auf die Fischbestande ausgewahlter bayerische Gewasser unter Berucksichtigung fishokologischer und fischereiokonomischer Aspekte Bayerische Landesanstalt fur Fischerei, Starnberg.


12 June 2012

Kenward RE. 1982. Goshawk predation on pheasants. Natural Environment Research Council Institute of Terrestrial Ecology Annual Report. pp83-84.

Kenward RE. 1986. Problems of goshawk predation on pigeons and some other game. Proc. XVIII International Ornithological Congress: 666-678.

Kenward RE. 1999. Raptor predation problems and solutions. Journal of Raptor Research 33(1): 73-75.

Kenward R. 2002. Management tools for reconciling bird hunting and biodiversity. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB). http://digital.csic.es/bitstream/10261/8264/1/Wp4-reportf.PDF

Kenward RE, Marcstrom V. 1981. Goshawk predation in game and poultry: some problems and solutions. Pages 152-162 in R.E. Keward and I. Lindsay, eds. Understanding the goshawk. International Association for Falconry and Conservation of Birds of Prey.

Kenward RE, Hall DG, Walls SS, Hodder KH, Pahkala, M. Freeman SN, Simpson VR. 2000. The prevalence of non-breeders in raptor populations: evidence from rings, radio-tags and transect surveys. Oikos, 91(2): 271-279.

Kenward RE, Hall DG, Walls SS, Hodder KH. 2001a. Factors affecting predation by buzzards Buteo buteo on released pheasants Phasianus colcchicus. Journal of Applied Ecology 38: 813-822.

Kenward RE, Hall DG, Walls SS, Hodder KH. 2001b. Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances. Journal of Animal Ecology 70:1-13.

Kevan SD. 1992. A review of methods to reduce bird predation on land-based fish farms. http://www.aps.uoguelph.ca/~aquacentre/aec/publications/control.html

Kirby JS, Holmes JS, Sellers RM. 1996. Cormorants (Phalacrocorax carbo) as fish predators: an appraisal of their conservation and management in Great Britain. Biological Conservation 75: 191-199.

Krebs JR, Cowie, RJ. 1976. Foraging strategies in birds. Ardea 64: 98-116. Larsen KH, Dietrich JH. 1970. Reduction of a raven population on lambing grounds with

DRC-1339. Journal of Wildlife Management 34(1): 200-204.

Leif AP. 1994. Survival and reproduction of wild and pen-reared ring-necked pheasant hens. Journal of Wildlife Management 58(3): 501-506.

Linnell JDC, Aanes R, Swenson JE, Odden J, Smith ME. 1997. Translocation of carnivores as a method for managing problem animals: a review. Biodoversity and Conservation 6:1245-1247. http://www.springerlink.com/content/gh7354725t5g8388/fulltext.pdf

Littauer G. 1990. Frightening techniques for reducing bird damage at aquaculture facilities. SRAC Publication No. 401. Southern Regional Aquaculture Center.

Lloyd DEB. 1976a. Avian predation of reared pheasants. Unpublished report for the British Field Sports Society, The Game Conservancy, The RSPB and the Wildfowlers Association of G.B. and Ireland. 84pp.

Lloyd DEB. 1976b. The protection of pheasants in release pens from birds of prey. Report to the British Field Sports Society, Game Conservancy, RSPB and Wildfowlers Association of Great Britain and Ireland. 12pp.


12 June 2012

Manosa S. 2002. The conflict between gamebird hunting and raptors in Europe. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB).

Marcstrom V., Kenward R. 1981. Movements of wintering goshawks in Sweden. Swedish Wildlife Research 12(1): 1-36.

Marquiss M, Newton I, Ratcliffe DA. 1978. The decline of the raven, Corvus corax, in relation to afforestation in southern Scotland and Northern England. Journal of Applied Ecology 15: 129-144.

Marquiss M, Madders M, Irvine J, Carss DN. 2003a. The impact of white-tailed eagles on sheep farming on Mull. ITE Contract No. ITE/004/99.

Marquiss M, Madders M, Carss DN. 2003b. White-tailed eagles (Haliaeetus albicilla) and lambs (Ovis aries). Pp. 471-479 in Birds of Prey in a Changing Environment (ed. Thompson DBA, Redpath SM, Fielding AH, Marquiss M and Galbraith CA). Scottish Natural Heritage, The Stationary Office, Edinburgh.

Marr NV, Edge WD, Anthony RG, Valburg R. 1995. Sheep carcass availability and use by bald eagles. Wilson Bulletin 107(2): 251-257.

Martin TE. 1993. Nest predation among vegetation layers and habitat types: revising the dogmas. American Naturalist, 141: 897-913.

Mason JR. 2001. Management alternatives relative to predators. The role of predator control as a tool in game management. Extension publication SP-113 Kerrville, texas, April 18th-19th, 2001. Pp 144-157. http://texnat.tamu.edu/symposia/RoleofPredatorControl/020.pdf

Mason JR and Clark L. 1997. Avian repellents: options, modes of action and economic considerations. Repellents in Wildlife Management (ed. J.R. Mason), pp. 371-391. Colorado State University, Fort Collins, CO.

Massei G, Quy RJ, Gurney J, Cowan DP. 2010. Can translocations be used to mitigate human-wildlife conflicts? Wildlife Research 37: 428-439.

Matchett MR, O'Gara BW. 1987. Methods of controlling Golden Eagle depredation on domestic sheep in Southwestern Montana Journal of Raptor Research 21(3): 85-94.

McKay HM, Furness R, Russell I, Parrott D, Rehfisch M, Watola G, Packer J, Armitage M, Gill E, Robertson P. 1999. The assessment of the effectiveness of management measures to control damage by fish-eating birds to inland fisheries in England and Wales. Report to the Ministry of Agriculture, Fisheries and Food (MAFF Project VC0107).

McKeaney TP, Jenkins AM. 1983. Bald eagle predation on domestic sheep. Wilson Ornithological Society, 95(4): 694-695.

McLean B, Jones M, Frosr D. Undated. Woodland Poultry and Pigs: Feasibility study into the potential of incorporating poultry and pigs into woodland management for producers in Powys. ADAS Report. www.glasu.org.uk/en/.../WoodlandPigs&PoultryFeasibilityStudy.pdf

McNamara K, O’Kiely P, Whelan J, Forristal PD, Lenehan JL. 2002. Preventing bird damage to wrapped baled silage during short- and long-term storage. Wildlife Society Bulletin 30(3): 809-815

McNeal LG. Sheep sheet. Undated. The Navajo Sheep project. http://navajosheepproject.com/images/pdf/llamas.pdf


12 June 2012

Mearns R. 1982. Winter occupation of breeding territories and winter diet of Peregrines in South Scotland. Ornis Scandinavica, 13: 79-83.

Miner NR. 1975. Montana golden eagle removal and translocation project. Proc. Great Plains Wildlife Damage Control Workshop. Pp 155-162. http://digitalcommons.unl.edu/gpwdcwp/201/

Moberly RL, White PCL, Webbon CC, Baker PJ, Harris S. 2003. Factors associated with fox (Vulpes vulpes) predation of lambs in Britain. Wildlife Research 30: 219-227.

Murphy JR. 1977. Eagles and livestock – some management considerations. World Conference on Birds of Prey 1975. pp 307-314.

Musgrove A. 1996. Peregrines and pigeons: investigations into a raptor-human conflict. PhD thesis, University of Bristol.

Musgrove A. 1998. Peregrines and Pigeons (again!). BTO News, 214: 11.

Naef-Daenzer L. 1983. Scaring of carrion crows (Corvus corone corone) by species-specific distress calls and suspended bodies of dead crows. Proceedings 9th Bird Control Seminar. Bowling State Green University, Bowling Green, Ohio.

Nakamura K. 1997. Estimation of the effective area of bird scarers. Journal of Wildlife Management 61(3): 925-934.

Nash MI, Hungerford II, Nash TG, Zinn GM. 1996. Risk factors for perinatal and postnatal mortality in lambs. Veterinary Record 139: 64-67.

National Farmers Union. (NFU) (Undated). Bird Scarers Code of Practice.

Nemtzov SC, Galili E. 2006. A new wrinkle on an old method: successful use of scarecrows as a non-lethal method to prevent bird damage to field crops in Israel. In: Timm, RM et al. (Ed.). Proceedings of the 22nd vertebrate pest conference pp. 222-224. Univ. of Calif., Davis.

Newton I. 1975. Movements and mortality of British sparrowhawks. Bird Study 22(1): 35-43. Newton I. 1993. Predation and limitation of bird numbers. Current Ornithology 11:143-197.

Newton I. 1998. Population limitation in birds. Academic Press, San Diego, USA.

Newton I. 1986. The Sparrowhawk. Poyser, Calton. Newton I, Davis PE, Davis JE. 1982. Ravens and buzzards in relation to sheep-farming and

forestry in Wales. Journal of Applied Ecology 19: 681-706.

Newton I, Marquiss M. 1982. Food, predation and breeding season in sparrowhawks (Accipiter nisus). J. Zool. Lond. 197: 221-240.

Newton I, Marquiss M. 1983. Dispersal of sparrowhawks between birthplace and breeding place. Journal of Animal Ecology 52: 463-477.

Newton I, Marquiss M. 1991. Removal experiments and the limitation of breeding density in sparrowhawks. Journal of Animal Ecology 60: 535-544.

National Farmers Union (NFU) (Undated). Bird Scarers Code of Practice.

Nicholls MK, Love OP, Bird DM. 2000. An evaluation of methyl anthranilate, aminoacetophenone, and unfamiliar coloration as feeding repellents to American kestrels. Journal of Raptor Research 34(4): 311-318.

Nicolaus LK, Cassel JK, Carlson RB, Gustavson CR. 1982. Taste-aversion conditioning of crows to control predation on eggs. Science 220: 212-214.

Nicolaus LK. 1987. Conditioned aversions in a guild of egg predators: implications for aposematism and prey defense mimicry. American Midland Naturalist 117(2): 405-419.


12 June 2012

Nicolaus LK, Farmer PV, Gustavson CR, Dimmick CR. 1989a. The potential of estrogen-based conditioned taste aversion in controlling depredation: a step closer towards the ‘Magic Bullet’. Applied Animal Behaviour Science 23: 1-14.

Nicolaus LK, Herrera J, Nicolaus JC, Dimmick CR. 1989b. Carbachol as a conditioned taste aversion agent to control avian depredation. Agriculture, Ecosystems and Environment 26: 13-21.

Nicolaus LK, Herrera J, Nicolaus JC, Gustavson CR. 1989c. Ethinyl estradiol and generalised aversions to eggs among free ranging predators. Applied Animal Behaviour Science 24: 313-324.

Niemeyer C. 1977. Montana Golden Eagle removal and translocation project. Final report. In Great Plains Wildlife Damage Control Workshop Proceedings, University of Nebraska, Lincoln, pp. 155-162.

Norberg H, Kojola I, Aikio P, Nylund M. 2005. Predation by golden eagle Aquila chrysaetos on semi-domesticated reindeer Rangifer tarandus calves in northeastern Finnish Lapland. Wildlife Biology 12:393-402.

Nordstrom M. 2003. Introduced predator in Baltic sea archipelagos: variable effects of feral mink on bird and small mammal populations. 118 p. Turun Yliopisto, Turku.

Nyhus PJ, Osofsky SA, Ferraro P, Madden F, Fischer H. 2005. Bearing the costs of human-wildlife conflict: the challenges of compensation schemes. Pp 107-121 In: Woodroffe R, Thirgood, S and Rabinowitz A (eds) Conservation Biology 9: People and Wildlife. Conflict or Coexistence?. Cambridge University Press.

O’Connor, R.J. 1991. Long-term bird population studies in the US. Ibis 133: s30-s48. O’Gara BW, Rightmire W. 1987. Wolf, golden eagle and coyote problems in Montana. Proc.

3rd Eastern Wildlife Damage Control Conference. University of Nebraska, Lincoln. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1041&context=ewdcc3

O’Gara BW. 1994. Eagles. Pp E41-E48 In: The Handbook: Prevention and control of wildlife damage. Internet Center for Wildlife Damage Management. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1059&context=icwdmhandbook

O’Toole L, Fielding AH, Haworth PF. 2002. Re-introduction of the Golden Eagle into the Republic of Ireland. Biological Conservation 103: 303-312.

Omerod SJ. 2002. Applied issues with predators and predation: editor’s introduction. J. Applied Ecology 39:181-188.

Oro D, Tella JL. 1995. A comparison of two methods for studying the diet of the peregrine falcon. Journal of Raptor Research, 29: 207-210.

Owens NW. 1976. Responses of wintering Brent geese to human disturbance. Wildfowl 28: 5-14.

Packer JJ, Birks JD. 1999. An assessment of British farmers’ and gamekeepers’ experiences, attitudes and practices in relation to the European polecat Mustela putorius. Mammal Review 29:75-92.

Palma L, Beja P, Pais M, Cancella da Fonesca L. 2006. Why do raptors take domestic prey? The case of the Bonelli’s eagles and pigeons. J ournal of Applied Ecology 43: 1075-1086.

Parish DMB, Sotherton N. 2007. The fate of released captive-reared grey partridges Perdix perdix: implications for reintroduction programmes. Wildlife Biology 13(2): 140-149.


12 June 2012

Park KJ, Calladine JR, Graham KE, Stephenson CM, Wernham CV. 2005. The Impacts of Predatory Birds on Waders, Songbirds, Gamebirds and Fisheries Interests. Report to the Scotland’s Moorland Forum.

Park KJ, Graham KE, Calladine J, Wernham CW. 2008. Impacts of birds of prey on gamebirds in the UK: a review. Ibis 150 (Suppl. 1): 9-26.

Parkhurst JA, Brooks RP, Arnold DE. 1987. A survey of wildlife depredation and control techniques at fish-rearing facilities. Wildlife Society Bulletin 15: 386-394.

Parrott D., McKay HV, Watola GV, Bishop JD, Langton, S. Effects of a short-term shooting program on non-breeding cormorants at inland fisheries. Wildlife Society Bulletin 31(4): 1092-1098.

Pembrokeshire Bird Group 2006. Lyndon’s Monthly roundup. Pembrokeshire Bird Group 2006.

Phillips RL, Sheridan Blom F. 1988. Distribution and magnitude of eagle/livestock conflicts in the western United States. Proc. 13th Vertebrate Pest Conference, 241-244. University of Nebraska. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1048&context=vpcthirteen

Phillips RL, Cummings JL, Berry JD. 1991. Responses of breeding golden eagles to relocation. Wildl. Soc. Bull. 19:430-434.

Pochop PA, Johnson RJ, Agüero DA, Eskridge KM. 1990. The status of lines in bird damage control – a review. Proceedings 14th Vertebrate Pest Conference, pp 317-324. University of California, Davis.

Prather PR, Messmer TA. 2010. Raptor and corvid response to power distribution line perch deterrents in Utah. Journal of Wildlife Management 74(4): 796-800.

Rantanen E, Buner F, Riordan P, Sotherton NW, Macdonald DW. 2010a. Vigilance, time budgets and predation risk in reintroduced captive-bred grey partridge Perdix perdix. Applied Animal Behaviour Science 127:43-50.

Rantanen E, Buner F, Riordan P, Sotherton NW, Macdonald DW. 2010b. Habitat preferences and survival in wildlife reintroductions: an ecological trap in reintroduced grey partridges. Journal of Applied Ecology 47: 1357-1364.

Ratcliffe D. 1962. Breeding density in the peregrine Falco perigrinus and raven Corvus corax. Ibis 104: 13-39.

Ratcliffe D. 1997. The Raven: A Natural History in Britain and Ireland. T & AD Poyser, London.

Redpath S, Thirgood S. 1997. Birds of prey and red grouse. London: Stationery Office.

Redpath SM, Clarke R, Madders M, Thirgood SJ. 2001. Assessing raptor diet: comparing pellets, prey remains, and observational data at harrier nests. The Condor 103: 184-188.

Redpath SM, Arroyo BE, Bayfield N, Bacon P, Thirgood, Gutiérrez RJ. 2002. Towards a resolution of the raptor-grouse conflict in upland Britain – the application of decision modelling with stakeholders. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB).

Redpath SM, Arroyo BE, Leckie FM, Bacon P, Bayfield N, Gutiérrez RJ, Thirgood SJ. 2004. Using decision modelling with stakeholders to reduce human-wildlife conflict: a raptor - grouse case study. Conservation Biology: 18 350-359.

Reif V, Tornberg T. 2006. Using time-lapse digital video recording for a nesting study of birds of prey. European Journal of Wildlife Research 52: 251-258.


12 June 2012

Risely K, Noble DG, Baillie SR. 2008. The Breeding Bird Survey 2008. BTO Research Report 508. British Trust for Ornithology, Thetford.

Risely K, Renwick AR, Dadam D, Eaton MA, Johnston A, Baillie SR, Musgrove AJ, Noble DG. 2011. The Breeding Bird Survey 2010. BTO Research Report 597. British Trust for Ornithology, Thetford.

Robertson PA. 1988. Survival of released pheasants, Phasianus colchicus, in Ireland. J. Zool., Lond. 214:683-695.

Robertson PA, Woodburn MIA, Hill DA. 1993a. Factors affecting winter pheasant density in British woodlands. Journal of Applied Ecology 30: 459-464.

Robertson PA, Woodburn MIA, Neutel W, Bealey CE. 1993b. Effects of land use on breeding pheasant density. Journal of Applied Ecology 30: 465-477.

Sage RB, Ludolf C, Robertson PA. 2005. The ground flora of ancient semi-natural woodland in pheasant release pens in England. Biological Conservation 122: 243-252.

Salmon TP, Conte FS. 1981. Control of bird damage at aquaculture facilities. Wildlife Management Leaflet, U.S. Fish and Wildlife Service.

SASA 2010. Raven Predation: A Guide for Farmers. Sayre RW, Clark L. 2001. Effect of primary and secondary repellents on European starlings:

an initial assessment. Journal of Wildlife Management 65(3): 461-469.

Schmidt RH, Johnson RJ. 1983. Bird dispersal recordings: an overview. Vertebrate Pest Control and Management Mateials: Fourth Symposium, ASTM STP 817, (ed. D.E. Kaukeinen), pp. 43-65. American Society for Testing and Materials, Philadelphia.

Schofield T. 2009. White-tailed Eagle proposed reintroduction project: livestock impacts and mitigation assessment. Farming and Wildlife Advisory Group report to Natural England.

Schreiber A, Stubbe A, Stubbe M. 2001. Common buzzard (Buteo buteo): A raptor with hyperpolymorphic plumage morphs, but low allozyme heterozygosity. Journal fur Ornithologie 142: 34-48.

Scottish Homing Union (SHU). 1998. Attacks by peregrines & sparrowhawks on racing pigeons in Scotland. 29pp. Hamilton, SHU.

Seamans TW. 2004. Response of roosting Turkey vultures to vulture effigies. Ohio Journal of Science 104(5):136-138. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1380&context=icwdm_usdanwrc

Seamans TW, Hicks CR, Preusser KJ. 2007. Dead bird effigies: a nightmare for gulls. pp 1-10. Bird Strike Committee Proceedings. 2007 Bird Strike Committee USA/Canada 9th Annual Meeting, Kingston, Ontario. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1014&context=birdstrike2007

Shivik JA 2004. Non-lethal alternatives for predation management. Sheep & Goat Research Journal 19:64-71.

Shivik JA. 2006. Tools for the edge: what’s new for conserving carnivores. Bioscience 56(3):253-259.

Sih A, Crowley P, McPeek M, Petranka J, Strohmeier K. 1985. Preadtion, competition, and prey communities. Annual Review of Ecology and Systematics 16: 269-311.

Simm G, Connington J, Bishop SC, Dwyer CM, Pattinson S. 1996. Genetic selection for extensive conditions. Applied Animal Behaviour 49: 47-59.


12 June 2012

Simms IC, Ormston CM, Somerwill KE, Cairns CL, Tobin FR, Judge J, Tomlinson A. 2010. A pilot study into sea eagle predation on lambs in the Gairloch area – Final Report. Scottish Natural Heritage Commissioned Report No. 370.

Smith AE, Craven SR, Curtis PD. 1999 Managing Canada geese in urban environments. Jack Berryman Institute Publication 16, and Cornell University Cooperative Extension, Ithaca, N.Y.

Smith RK, Pullin AS, Stewart GB, Sutherland WJ. 2010. Effectiveness of predator removal for enhancing bird populations. Conservation Biology 24(3): 820-829.

SNH. 2004. The Mull Eagle Scheme. http://www.scottishfossilcode.org/pdfs/NatCare/Mull%20EagleSchem.pdf

SNH 2006. Sea Eagle Management Scheme. Information Sheet – 13th January 2006. SNH. 2009a. The Common Buzzard.

http://www.snh.org.uk/licences/li-advguide.asp

SNH. 2009b. The Northern Raven. http://www.snh.org.uk/licences/li-advguide.asp

SNH. 2009c. The Eurasian Sparrowhawk. http://www.snh.org.uk/licences/li-advguide.asp

Stahl P, Ruette S, Gros L. 2002. Predation on free-ranging poultry by mammalian and avian predators: field loss estimates in a French rural area. Mammal Review 32(3): 227-234.

Stucky JT. 1973. Use of plastic netting. Proc. Bird Control Seminar 6: 195-197. Swan G. 2011. Spatial Variation in the Breeding Success of the Common Buzzard Buteo

Buteo in relation to Habitat Type and Diet. Unpublished MSc thesis, Imperial College, University of London, London.

Tapper S. 2007. Potential solutions to the grouse/hen harrier conflict.

Thirgood S, Redpath S, Newton I, Hudson P. 2000. Raptors and red grouse: conservation conflicts and management solutions. Conservation Biology 14(1): 95-104.

Thirgood S, Redpath SM, Campbell S, Smith A. 2002. Do habitat characteristics influence predation on red grouse? Journal of Applied Ecology 39: 217-225.

Thirgood S, Redpath S. 2005. Hen harriers and red grouse: the ecology of a conflict. Pp192-208. In: Woodroffe R, Thirgood, S and Rabinowitz A (eds) Conservation Biology 9: People and Wildlife. Conflict or Coexistence? Cambridge University Press.

Thirgood S, Redpath S. 2008. Hen harriers and red grouse: science, politics and human–wildlife conflict. Journal of Applied Ecology Volume 45(5):1550-1554. http://www3.interscience.wiley.com/cgi-bin/fulltext/121376684/PDFSTART

Tilman EA, Van Doom Annamaria, Avery ML. 2000. Bird damage to tropical fruit in South Florida. Wildlife Damage Management, Internet Center for Wildlife Damage Management Conferences – Proceedings. University of Nebraska, Lincoln.

http://digitalcommons.unl.edu/icwdm_wdmconfproc/13

Tobin ME, Woronecki PP, Dolbeer RA, Bruggers RA. 1988. Reflecting tape fails to protect ripening blueberries from bird damage. Wildlife Society Bulletin 16(3): 300-303.

Tornberg R, Leif V. 2007. Assessing the diet of birds of prey: a comparison of prey items found in nests and images. Ornis Fennica 84: 21-31.

Transport Canada. 1994. Bird dispersion techniques and their effectiveness. Control Procedures Manual. http://www.tc.gc.ca/aviation/aerodrome/birdstke/main.htm


12 June 2012

Turner CV. 2007. The Fate and Management of Pheasants (Phasianus colchicus) Released in the UK. Unpublished PhD Thesis. Imperial College, University of London, London.

Turner C, Sage R. 2003. Fate of released pheasants. The Game Conservancy Trust Review 35, 74-75.

Valkama J, Korpimaki E, Arroyo B, Beja P, Bretagnolle V, Bro E, Kenward R, Manosa S, Redpath SM, Thirgood S, Vinuela J. 2005. Birds of prey as limiting factors of gamebird populations in Europe: a review. Biological Reviews 80:171-203.

Vaudry AL. 1979. Bird control for agricultural lands in British Columbia. Publications – British Columbia Ministry of Agriculture 78-21. 19pp.

Vickery JA, Summers RW. 1992. Cost-effectiveness of scaring brent geese Branta b. bernicla from fields of arable crops by a human bird scarer. Crop Protection 11: 480-484.

Vinuela J, Arroyo B. 2002. Gamebird hunting and biodiversity conservation: synthesis, recommendations and future research priorities. European Concerted Action within the 5th Framework Program: Reconciling Gamebird Hunting and Biodiversity (REGHAB).

Wade DA. 1980. Predator damage control, 1980: recent history and current status. Proc. 9th Vertebrate Pest Conference, 189-199. University of California, Davis, California. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1039&context=vpc9

Wade DA, Hawthorne DW, Nunley GL, Milton C. 1984. History and status of predator control in Texas. Proc. 11th Vertebrate Pest Conference, 121-131. University of California, Davis, California. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1041&context=vpc11

Wade DA. 1986. Predator damage control: 1980 to 1986. Proc. 12th Vertebrate Pest Conference, 369-386. University of California, Davis, California. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1062&context=vpc12

Wagner KK, Schmidt RH, Conover MR. 1997. Compensation programmes for wildlife damage in North America. Wildlife Society Bulletin 25:312-319.

Waite BC, RL Phillips. 1994. An approach to controlling golden eagle predation on lambs in South Dakota. Proceedings of the Vertebrate Pest Conference 16:28-30.

Walls SS, Kenward RE. 1995. Movements of radio-tagged Common Buzzards Buteo buteo in their first year. Ibis 137(2): 177–182.

Warner M. 2000. Conflict Management in community-based natural resource projects: Experiences from Fiji and Papua New Guinea. Working Paper 135. Overseas Development Institute 2000.

Warren JT, Mysterud I, Lynnebakken T. 2001. Mortality of lambs in free-ranging domestic sheep (Ovis aries) in northern Norway. J. Zool. Lond. 254: 195-202. http://journals.cambridge.org/download.php?file=%2FZOO%2FZOO254_02%2FS095283690100070Xa.pdf&code=546ae5f32ec3d9787ed3eff3d6c22b2f

Watte BC, Phillips RL. 1994. An approach to controlling golden eagle predation on lambs in South Dakota. Proc. 16th Vertebrate Pest Conference, 28-30. University of California, Davis, California. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1065&context=vpc16

White PCL, Groves HL, Savery JR, Connington J, Hutchings MR. 2000. Fox predation as a cause of lamb mortality on hill farms. Veterinary Record 147: 33-37.

Whitfield P. 2000. Golden eagle Aquila chrysaetos ecology and conservation issues. Scottish Natural Heritage Review No. 132.


12 June 2012

Wilbanks CA. (undated). Alternative methods of predator control. http://texnat.tamu.edu/symposia/coyote/p33.htm

Wilson JD, Weir AG. 1989. Hunting behaviour and attack success of a female sparrowhawk between October 1987 and April 1988. Scottish Birds 15: 126-130.

Woodruff RA, Green JS. 1995. Livestock herding dogs: a unique application for wildlife damage management. Pp 43-45 In: RE Masters and JC Huggins (eds). 12th Great Plains Wildl. Damage Control Workshop Proc., Noble Foundation, Ardmore, Okla. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1002&context=icwdmsheepgoat


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Appendix I. Raptor management documents reviewed.

‘EFFECTIVE? = view of the reference author/s

No. REFERENCE LIVESTOCK BIRD PREDATORS MAMMAL PREDATORS MEASURE EFFECTIVE? COUNTRY SITE

1. ALBERTA SHEEP & WOOL

COMMISSION 2007 SHEEP

BALD EAGLE

GOLDEN EAGLE

DOG, COYOTE, WOLF,

BEAR, COUGAR

ELECTRIC FENCING, GUARDIAN

ANIMALS, REMOVE DEAD

LIVESTOCK, PROPANE EXPLODERS,

SIRENS, DISTRESS CALLS, LIGHTS,

SCARECROWS, RADIO, PREDATOR

REDUCTION

VARIED USA PASTURE

2. ALLAN ET AL. 2000

SEE TABLE 9.1 PHEASANT BUZZARD UNIDENTIFIED

MYLAR TAPE, LIGHTS & MIRRORS,

HANGING BAGS VARIED UK RELEASE PENS

3. ALLAN 2001

SEE TABLE 9.1 PHEASANT

BUZZARD, SPARROWHAWK,

TAWNY OWL FOX

MYLAR TAPE, LIGHTS & MIRRORS,

HANGING BAGS VARIED UK RELEASE PENS

4. ANDELT 2004 SHEEP, CATTLE, GOATS GOLDEN EAGLE

COYOTE, DOG,

MOUNTAIN LION, BLACK

BEAR, RED FOX, BOBCAT

GUARDIAN ANIMALS –

DOG, DONKEY, LLAMA YES USA

FENCED PASTURE,

OPEN RANGE

5. ANDELT & HOPPER 2000 SHEEP GOLDEN EAGLE

COYOTE, DOG,

MOUNTAIN LION, BLACK

BEAR

GUARDIAN DOGS YES USA FENCED PASTURE,

OPEN RANGE

6. ASHEIM & EIK 2005 SHEEP GOLDEN EAGLE BROWN BEAR, WOLF,

LYNX, WOLVERINE

HUSBANDRY,

COMPENSATION

VARIED,

UNDER DEVELOPMENT NORWAY

INDOOR, FENCED

PASTURE,

OPEN RANGE

7. AVERY & CUMMINGS 2004 PIGS, LAMBS, POULTRY GOLDEN EAGLE

BLACK VULTURE NONE

HARASSMENT, HUSBANDRY,

CORPSES, RELOCATION,LETHAL VARIED USA VARIOUS

8. BASC 2009 GAME BIRDS UK RAPTORS NONE LICENSED REMOVAL, DESTRUCTION

AND TRANSLOCATION NOT TESTED UK VARIOUS

9. BASC (UNDATED) PHEASANTS UK RAPTORS NONE HABITAT MANAGEMENT, SCARING

DEVICES, HUSBANDRY YES UK RELEASE PENS

10. BERANGER (2007) TURKEYS EAGLES, HAWKS, OWLS AND

VULTURES

BOBCATS, CATS,

WOLVES, COYOTES,

DOGS, FOXES,

OPOSSUMS, PACK RATS,

RACCOONS, RATS,

SKUNKS, WEASELS AND

MINK

FENCING, HABITAT MANAGEMENT,

GUARDIAN ANIMALS, VISUAL

SCARING AND LETHAL CONTROL

NOT TESTED USA ENCLOSURES AND

EXCLOSURES

11. BOURNE 2001 POULTRY BIRDS OF PREY COYOTE

OVERHEAD WIRE MESH – OUTDOOR

PENS

“SHINY BOTTLE”

ELIMINATE RIGHT-ANGLED CORNERS

PARTIAL USA OUTDOOR PENS,

LARGE ENCLOSURES


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12. BUTCHKO 1990

PROTECTED SPECIES: SAN

JOAQUIN KIT FOX, LEAST

TERN AND DESERT

TORTOISE

KESTREL, LOGGERHEAD SHRIKE,

RAVEN, HARRIER, ROCK DOVE

AND BURROWING OWL

COYOTES, CAT, FOX,

GROUND SQUIRREL

RACCOON AND SKUNK

TRAPPING, SHOOTING, DENNING

AND POISON, YES USA VARIOUS

13. CADE 2000 NONE STATED

EAGLE, HAWKS, BUZZARDS,

KITES, HARRIERS, VULTURES,

FALCONS AND OWLS

NONE REVIEW OF TRANSLOCATION CONSERVATION – YES

CONFLICT - NO

USA,

CANADA,AFRIC

AEUROPE,

CENTRAL AND

S. AMERICA

VARIOUS

14. COATES ET AL. 2007 GAMEBIRDS RAVENS NONE TASTE AVERSION YES USA WOODLAND

15. COLORADO DIVISION OF WILDLIFE

(UNDATED) POULTRY AND PETS USA RAPTORS NONE ENCLOSURE YES USA NOT STATED

16. COPE ET AL. 2005 GRASS AND FODDER

CROPS GEESE NONE

CULLING, SCARING, SACRAFICIAL

CROPS, COMPENSATION VARIED UK

PASTURE AND

CROPS

17. COWAN ET AL. 2000 GROUSE, SHEEP +

OTHERS BUZZARDS AND BLUE JAYS

BEARS, COYOTES,

WOLVES, DINGO, SKUNK

AND RAT

CONDITIONED TASTE AVERSION YES USA VARIOUS

18. DAVIES 1999 SHEEP BLACK EAGLES AND MARTIAL

EAGLES NONE

HUSBANDRY, HUMAN

DISTURBANCE, FOOD AVERSION YES SOUTH AFRICA OPEN RANGE

19. DIMMICK & NICOLAUS 1990. WATERFOWL AND GAME

BIRDS CROWS NONE TASTE AVERSION YES USA WOODLAND

20. ENDANGERED WILDLIFE TRUSTS

WILDLIFE CONFLICT PREVENTION

GROUP

SHEEP BLACK EAGLES BLACK-BACKED JACKALS,

CARACAL ENCLOSURE, GUARD ANIMALS YES SOUTH AFRICA OPEN RANGE

21. ENVIRONMENT COUNCIL 2007 GROUSE HEN HARRIER NONE DIVERSIONARY FEEDING, SCARING,

TRAP AND TRANSFER NOT TESTED UK MOORLAND

22. DEPARTMENT OF ENVIRONMENT

AND CONSERVATION 2007A SHEEP WEDGE-TAILED EAGLE NONE

HUSBANDRY, SCARING AND

ALTERNATIVE FEEDING YES AUSTRALIA OPEN RANGE

23. FISCHER & LINDENMAYER 2000 NONE STATED VARIOUS VARIOUS REVIEW OF SUPPLEMENTATION AND

TRANSLOCATION

CONSERVATION – YES

CONFLICT - NO WORLD VARIOUS

24. GRAHAM ET AL. 2003 SHEEP, DEER, CATTLE,

GROUSE

GOSHAWK, BUZZARD, RED

KITE, HEN HARRIER

LYNX, WOLF, BEAR

BABOON, LEOPARD,

SNOW LEOPARD, LION,

PUMA, HUNTING DOG,

COYOTE, FOX AND

JACKAL

HUSBANDRY, HOME RANGE SIZE,

PREDATOR DENSITY AND HUMAN

POPULATION SIZE

NO WORLDWIDE VARIOUS

25. GREEN ET AL. 1984 SHEEP AND GOAT GOLDEN EAGLES

COYOTES, FERAL DOGS,

BEARS, PUMAS,

BOBCATS, WOLVES AND

FOX

GUARD DOGS YES USA PASTURE AND OPEN

RANGE


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26. HYGNSTROM & CRAVEN 2005 FREE RANGE POULTRY,

GAME FARM FOWL

GOSHAWK, RED-TAILED HAWK

AND GREAT-HORNED OWL NONE

EXCLUSION, HABITAT

MODIFICATION, SCARING,

REPELLENTS, TRAPPING,

TRANSLOCATION, SHOOTING

NOT TESTED USA VARIOUS

27. KENWARD 1999

SHEEP, POULTRY,

PIGEONS, GAME

TETRAONIDS AND

SEABIRDS

HAWKS, EAGLES AND FALCONS NONE

EXCLUSION, LANDSCAPING,

DETERRENCE, COMPENSATION AND

RELOCATION

VARIED WORLDWIDE VARIOUS

28. KENWARD 2002 LIVESTOCK, POULTRY

AND GAME

GOLDEN EAGLE, IMPERIAL

EAGLE, BOOTED EAGLE

GOSHAWK, SPARROWHAWK,

BUZZARD, RED KITE, BLACK

KITE, MARSH HARRIER, HEN

HARRIER, PEREGRINE, EAGLE

OWL

NONE

EXCLUSION, LANDSCAPING,

DETERRENCE, PRE-EMPTIVE

CONTROL, TRANSLOCATION,

INTRODUCED TOP-PREDATORS,

COMPENSATION

VARIED EUROPE VARIOUS

29. KENWARD ET AL. 2002 PHEASANTS BUZZARDS NONE HUSBANDRY AND HABITAT

MANAGEMENT YES UK ENCLOSURES

30. LINNELL ET AL. 1997 VARIOUS EAGLES URSIDS, CANIDS, FELIDS

AND MUSTELIDS TRANSLOCATION NO

USA EUROPE

SOUTHERN

AFRICA

OPEN RANGE

31. LLOYD 1976

SEE TABLE 9.1 PHEASANTS

BUZZARD, SPARROWHAWK,

TAWNY OWL FOX

HANGERS, VARIOUS LIGHTS, FLADRY,

MIRRORS, SCARECROWS, BANGERS,

STRINGS, NETTING, DOUBLE-

PENNING, DECOY FEEDING

VARIED

UK RELEASE PENS

32. MARQUISS ET AL. 2003A SHEEP WHITE-TAILED EAGLE NONE CLOSE-SHEPHERDING, SCARING AND

ALTERNATIVE FOOD NOT TESTED UK HILL COUNTRY

33. MACHETT & O’GARA 1987 SHEEP GOLDEN EAGLE NONE TRANSLOCATION, HARASSMENT,

DETERRENTS AND HARASSMENT VARIED USA

HILLS AND OPEN

RANGE

34. MARR ET AL. 1995 SHEEP BALD EAGLE NONE NONE TESTED N/A USA MIXED FARMLAND

AND WOODLAND

35. MASON 2001 SHEEP, GAME AND

POULTRY RAVENS AND CROWS

COYOTE, PUMA,

RACOONS AND SKUNK

REVIEW OF NON-LETHAL – GUARD

ANIMALS, HUSBANDRY, HABITAT,

FENCING, FLADRY, ELECTRONIC

DEVICES, REPELLENTS, TASTE

AVERSIONS AND FERTILITY

TREATMENT

VARIED USA VARIOUS

36. MCEANEY & JENKINS SHEEP BALD EAGLE NONE NONE TESTED N/A USA OPEN RANGE

37. MINER 1975 SHEEP GOLDEN EAGLE NONE TRANSLOCATION NO USA OPEN RANGE

38. MURPHY 1977 SHEEP EAGLES NONE NONE TESTED N/A USA, EUROPE, PASTURE AND OPEN


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SOUTHERN

AFRICA,

AUSTRALIA

RANGE

39. NIICHOLLS ET AL. 2000. GAME BIRDS KESTREL NONE TASTE AVERSION

YES (BUT ONLY IN

ADDITION TO COLOUR

MANIPULATION)

USA CAGE

40. NICOLAUS ET AL. 1982. CHICKEN EGGS CROW NONE CONDITIONED TASTE AVERSION YES USA FIELD

41. NICOLAUS 1987. SURROGATE SANDHILL

CRANE EGGS

RAVENS

MAGPIES COYOTE CONDITIONED TASTE AVERSION YES USA FIELD

42. NIEMEYER 1977 SHEEP GOLDEN EAGLE NONE TRANSLOCATION NO USA OPEN RANGE

43. NORBERG ET AL. 2005 SEMI-DOMESTICATED

REINDEER GOLDEN EAGLE NONE NONE STATED N/A FINLAND ALPINE

44. O’GARA & RIGHTMIRE 1987 SHEEP GOLDEN EAGLES WOLVES, COYOTES TRAPPING, TRANSLOCATION,

SCARECROW SCARECROW- YES USA OPEN RANGE

45. O’GARA (UNDATED) SHEEP AND DEER GOLDEN AND BALD EAGLES NONE

EXCLUSION, HABITAT

MODIFICATION, HUSBANDRY,

SCARING

SCARECROW,

HUSBANDRY - YES USA

HILL SIDE, PASTURE

AND OPEN RANGE

46. O’TOOLE ET AL. 2002 SHEEP GOLDEN EAGLES NONE RE-INTRODUCTION INTO LOW

LIVESTOCK DENSITY HABITATS NOT KNOWN IRELAND HILL COUNTRY

47. OMEROD 2002 VARIOUS

BOOTED EAGLE, GOLDEN

EAGLE, BUZZARD, HEN HARRIER

AND SPARROWHAWK

LYNX, MINK, HEDGEHOG,

FERRET, FOX, WILDCAT,

DINGO

NONE STATED N/A WORLDWIDE VARIOUS

48. PALMA ET AL. 2006

FERAL PIGEONS, RACING

PIGEONS, DOMESTIC

FOWL

BONELLI’S EAGLE NONE DIVERSIONARY FOOD AND

HUSBANDRY NOT TESTED PORTUGAL HILL COUNTRY

49. PARK ET AL. 2008 GAME BIRDS HEN HARRIER, PEREGRINE,

SPARROWHAWK NONE NONE STATED N/A UK

UPLANDS AND

FARMLAND

50. PHILLIPS & BLOM 1988 SHEEP, GOATS AND

POULTRY

BALD EAGLE AND GOLDEN

EAGLE NONE

LIVE TRAP AND REMOVAL, LETHAL

CONTROL, SCARING AND OTHER INCONCLUSIVE USA OPEN RANGE

51. PHILLIPS ET AL. 1991 SHEEP GOLDEN EAGLE NONE TRANSLOCATION NO USA OPEN RANGE AND

PASTURE

52. PRATHER & MESSMER 2010 SAGE GROUSE GOLDEN EAGLE, RAVEN,

ROUGH-LEGGED HAWKS NONE PERCH DETERRENTS NO USA

OPEN RANGE AGRIC

FIELDS

53. REDPATH ET AL. 2004 RED GROUSE HEN HARRIER NONE

QUOTA SCHEMES, DIVERSIONARY

FOOD, PREDATOR CONTROL,

RAPTOR CONTROL, HABITAT

MANAGEMENT, PARASITE CONTROL

NOT TESTED UK UPLANDS

54. RSPB (UNDATED) RACING PIGEONS PEREGRINE AND

SPARROWHAWK NONE

ALTER RACE SCHEDULES,

HUSBANDRY, TASTE AVERSION NOT TESTED UK VARIOUS


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55. SEAMANS 2004 HUMAN ISSUES – BIRD

STRIKE AND H & S

TURKEY VULTURE AND BLACK

VULTURE NONE DEAD VULTURE EFFIGY YES USA NOT KNOWN

56. SEAMANS ET AL. 2007 HUMAN ISSUES – BIRD

STRIKE HAZARD

RING-BILLED GULL AND

HERRING GULL NONE DEAD GULL EFFIGIES VARIED USA VARIOUS

57. SHIVIK 2004 GENERAL NOT SPECIFIED NOT SPECIFIED NON-LETHAL METHODS VARIED USA VARIOUS

58. SHIVIK 2006 CATTLE, SHEEP AND

OTHERS BALD EAGLE, TURKEY VULTURE

BLACK BEAR, COYOTE,

WOLF

ELECTRONIC GUARD, FERTILITY

GUARD, FLADRY, GUARD DOG,

HAZING, TRANSLOCATION, TRAINING

COLLAR, RADIO OR MOVEMENT

ACTIVATED GUARD

YES USA VARIOUS

59. SNH 2004 SHEEP GOLDEN EAGLES

WHITE-TAILED SEA EAGLES NONE

COMPENSATION SCHEME FOR

HUSBANDRY, CLOSE SHEPHERDING,

PROTECTIVE LAMB JACKETS AND

HABITAT MANAGEMENT

NOT TESTED SCOTLAND HILL COUNTRY

60. SNH 2009A GAME BIRDS BUZZARD NONE

COVER, ENCLOSURE, VISUAL

DETERRENTS, DIVERSIONARY

FEEDING

NOT TESTED SCOTLAND VARIOUS

61. SNH 2009B SHEEP RAVEN NONE HUSBANDRY AND CLOSE

SHEPHERDING YES SCOTLAND HILLS

62. SNH 2009C RACING PIGONS SPARROWHAWK NONE NONE STATED N/A SCOTLAND VARIOUS

63. TAPPER 2007 GROUSE HEN HARRIER NONE

HABITAT MANAGEMENT,

DIVERSIONARY FEEDING,

INTRAGUILD PREDATION, NESTING

QUOTAS, TRANSLOCATION,

HUSBANDRY, TASTE AVERSION,

SCARING

UNTESTED UK MOORLAND AND

UPLANDS

64. THIRGOOD ET AL. 2002 RED GROUSE HEN HARRIER AND PEREGRINE NONE HABITAT MANAGEMENT NO UK MOORLAND

65. THIRGOOD & REDPATH 2005 RED GROUSE HEN HARRIER AND PEREGRINE NONE DIVERSIONARY FEEDING, FIXED

QUOTAS AND TRANSLOCATION NOT TESTED UK MOORLAND

66. THIRGOOD & REDPATH 2008 RED GROUSE HEN HARRIER NONE DIVERSIONARY FEEDING, FIXED

CEILING DENSITY NOT TESTED UK MOORLAND

67. WADE ET AL. 1984 SHEEP AND GOATS GOLDEN EAGLES, BLACK

VULTURE, TURKEY VULTURE

PUMA, BOBCATS,

WOLVES, COYOTES,

BEARS, FOXES, DOGS

ANIMAL DAMAGE CONTROL

PROGRAM, HUSBANDRY,

ENCLOSURE, SCARING, SHOOTING,

TRAPPING, POISON BAITS

UNSTATED USA VARIOUS

68. WADE 1986 SHEEP GOLDEN EAGLES

BALD EAGLES

COYOTES, BEAR, PUMA,

DOGS

ANIMAL DAMAGE CONTROL POLICY,

PREDATOR REMOVAL, SCARING,

HARASSMENT, EXCLUSION, GUARD

ANIMALS AND TOXIC COLLARS

VARIED USA VARIOUS


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69. WARREN ET AL. 2001 SHEEP GOLDEN EAGLE FOX, LYNX, WOLVERINE NONE STATED N/A NORWAY ALPINE

70. WATTE & PHILLIPS 1994 SHEEP GOLDEN EAGLE NONE TRANSLOCATION YES USA OPEN RANGE

71. WHITFIELD 2000 SHEEP GOLDEN EAGLE NONE ALTERNATIVE PREY, HUSBANDRY,

CARCASS REMOVAL NOT TESTED UK UPLANDS

72. WILBANKS (UNDATED) SHEEP AND GOATS GOLDEN EAGLE COYOTES, FERAL DOGS,

BOBCATS, FOXES, HOGS

GUARD ANIMALS, REPELLENTS,

DETERRENTS, AVERSION,

HUSBANDRY

VARIED USA VARIOUS


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Appendix II. Avian control techniques used against raptors

Target Category Technique Country Effective Notes

Ra

pto

r

Vis

ua

l Human-scarer UK, USA, S. Africa Yes

Close shepherding, labour intensive,

expensive.

Scarecrows USA, UK Varied

Effect short-term. . More effective if

combined with integrated

management strategy (IMS) and

harassment.

Corpses USA Varied Effect short-term; eventual

habituation.

Eye-spots/ balloons USA, Europe Varied Short-term effect. More effective if

combined with IMS and harassment.

Reflective

tape/mirrors/lights

UK

Europe Varied

Short-term effect. More effective if

combined with IMS and harassment.

Au

dit

ory

Pyrotechnics USA, Europe,

Africa, Australia Varied Short-lived effect. Best used with IMS.

Acoustics/Bioacoustics USA, Europe,

Africa, Australia Varied Best used with IMS.

Shooting to scare USA, Europe,

Africa, Australia Varied Short-lived effect. Best used with IMS.

Fe

ed

ing

Diversionary feeding USA, UK,

Australia Varied Requires thoughtful application.

Re

mo

ve

Translocation USA, Africa,

Europe Varied

Generally ineffective; raptors return to

where trapped or are replaced; some

evidence for effectiveness against

goshawks in Sweden.

Ch

em

ica

l

Conditioned Taste

Aversion (CTA) USA, UK Varied

Some success with corvids; but context

specific and results depend on

thoughtful application; requires

expensive development.

Fertility control USA (Yes)

Only tested on mammalian predators

and effective if predator’s reproductive

period coincides with lambing;

requires expensive development.

Leth

al

Shooting Worldwide No

Illegal and conservation constraints.

Net-gunning and translocation licensed

in USA as an alternative.

Egg destruction Worldwide No Illegal


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Target Category Technique Country Effective Notes

Nest destruction Worldwide No Illegal

Toxic USA, Australia,

Africa, Europe Varied

Illegal. Past impact varied; danger to

non-target species.

Quotas

Spain

Sweden

Europe

untested

Established for large carnivores in

Spain and Sweden; only discussed in

the literature for raptors.

Ha

bit

at

Exc

lusi

on

Fencing USA, Europe No Pens and buildings deterred eagles but

fencing did not.

Lines/Tapes USA, Europe Varied Protected poultry from hawks.

Pe

rch

av

ail

ab

ilit

y Perch removal/anti-

perch devices USA Varied Remove or prevent access to perches

Electrified perches USA unstated

Advocated to protect poultry and

game in pens and exclosures. Illegal in

UK.

Ha

bit

at

Vegetative

management USA, UK unstated

Advocated to improve alternative prey

abundance but can increase predator

densities; provides cover; reduces

suitable foraging/nesting habitat;

expensive.

Live

sto

ck

Ma

na

ge

me

nt

pra

ctic

es

Re-scheduling

production

USA, Africa,

Australia Yes

Coincide lambing with neighbours-

dilute impact, or time after migratory

departures.

Re-locating

production

Africa, Norway,

USA Yes

Move production away from nest sites;

locate birthing in protected areas or

indoors.

Improve

condition/production

USA, Africa,

Australia, UK Yes

E.g. keep new-borns in small

enclosures, provide supplementary

nutrients to ewes.

Shepherding/guard

animals USA, Africa Varied

Humans best. Geese can protect

smaller poultry from hawks. Dogs and

llamas ineffective against raptors.

Removal of fallen

stock USA, UK Yes

Reduces attractiveness of area to

predators.


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