saving a national icon: preliminary estimation of the ......suzie greenhalgh portfolio leader -...
TRANSCRIPT
Saving a national icon:
Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
John Innes1, Florian V. Eppink2
Landcare Research
Hugh Robertson3
Department of Conservation
Prepared for:
Kiwis for kiwi / The Kiwi Trust
Private Bag 68908 Auckland 1145
July 2015
1Landcare Research, Gate 10 Silverdale Road, University of Waikato Campus, Private Bag 3127, Hamilton 3240, New Zealand, Ph +64 7 859 3700, Fax +64 7 859 3701, www.landcareresearch.co.nz
2Landcare Research, 231 Morrin Road, St Johns, Private Bag 92170, Auckland 1142, New Zealand, Ph +64 9 574 4100, Fax +64 9 574 4101
3Department of Conservation, P.O. Box 10420, Wellington 6143, New Zealand
Reviewed by: Approved for release by:
Roger Pech Scientist Landcare Research
Suzie Greenhalgh Portfolio Leader - Enhancing Policy Development Landcare Research
Landcare Research Contract Report: LC2136
Disclaimer
This report has been prepared by Landcare Research for Kiwis for kiwi. If used by other parties, no warranty or representation is given as to its accuracy and no liability is accepted for loss or damage arising directly or indirectly from reliance on the information in it.
Landcare Research Page iii
Contents
Executive summary ..................................................................................................................... v
Glossary of key terms ................................................................................................................. vi
Summary ................................................................................................................................... vii
1 Introduction ....................................................................................................................... 1
2 Background ........................................................................................................................ 2
3 Objectives .......................................................................................................................... 2
4 Modelling kiwi recovery strategies ................................................................................... 2
4.1 Overview .............................................................................................................................. 2
4.2 Kiwi taxa and estimated 2015 population sizes .................................................................. 3
4.3 Current kiwi threats and management regimes, and resultant estimated population
growth rates ........................................................................................................................ 5
4.4 Modelling halting the decline and achieving 2% per annum growth ................................ 14
5 Estimating current and additional cost ........................................................................... 19
5.1 Cost data considerations ................................................................................................... 19
5.2 Annual cost of current management ................................................................................ 22
5.3 Additional cost of population stability and growth targets .............................................. 23
6 Discussion ........................................................................................................................ 31
6.1 Adequacy of input kiwi data .............................................................................................. 33
6.2 Kiwi modelling assumptions .............................................................................................. 33
6.3 Selecting growth scenarios and preferred management techniques ............................... 33
6.4 Community conservation and cost modelling ................................................................... 34
6.5 Additional funding required to halt declines and achieve 2% growth p.a. ....................... 35
6.6 Priority research and monitoring ...................................................................................... 36
7 Acknowledgements ......................................................................................................... 36
8 References ....................................................................................................................... 37
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page iv Landcare Research
Appendix 1: Explanation of key terms in this report ............................................................... 40
Appendix 2: Cost data and assumptions .................................................................................. 42
Landcare Research Page v
Executive summary
Kiwi conservation has been very successful since the Kiwi Recovery Programme was
launched in 1991. Much has been learned about kiwi and their threats; some tools have been
developed to grow kiwi populations; there is a groundswell of community and political
support to keep kiwi safe, and populations of the four rarest kiwi taxa are increasing.
However, substantial additional effort is required to reverse the overall potential decline of
2% per annum (without management) into a 2% increase across all 10 taxa (‘kinds’ of kiwi).
With the assumptions that kiwi conservation projects run by community groups ($6.3 million
of funded and donated costs) and by the Department of Conservation (DOC) remain at
current levels, and with new government funding of $6.8 million per year from 2018 onwards
as announced in Budget 2015, we estimate that all 10 kiwi taxa can be at least maintained at
current population levels. By our best modelled estimates, a further ca $1.3 million per year is
required across all kiwi to achieve an average of 2% per annum growth per year between now
and 2030. Using DOC staff instead of community volunteers, more aerial poisoning, and
allocating pest-fence costs to kiwi recovery will increase the estimated funding need.
Nationally, major challenges ahead include: a) reversing declines of those more abundant, but
steadily declining, kiwi taxa that live in remote and rugged parts of the South and Stewart
Islands, where human populations are small and remote from kiwi populations, and b) cost-
effectively monitoring the outcomes of management for all kiwi.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page vi Landcare Research
Glossary of key terms
Kiwi taxa (plural) and taxon (singular): For simplicity, we refer to the 10 different
‘kinds’ of kiwi (e.g. little spotted, Northland brown) as taxa, even though some are not
taxonomically described in scientific literature.
Management regime: There are seven active management regimes, such as pest
trapping, aerial poisoning or Operation Nest Egg, that are applied to kiwi populations to
increase their numbers.
Population growth rates: Kiwi populations are subject to annual change, depending on
nett outcomes of births and immigration versus deaths and emigration. We express
change rates either as (for example) 2% p.a. (so that each year the population is 2%
larger), or for modelling purposes, as 1.02. There may also be 2% p.a. declines, which
we express for modelling as 0.98.
Modelling parameters: Population modelling in this report uses (for each taxon) an
initial population size and subsequent growth rates that may differ for each
management regime, but population size and growth rates are both imperfectly known.
Therefore, we model these possible errors by choosing between most likely, or high and
low (e.g. ±30%) values of modelling parameters.
Conservation scenarios: These are combinations of management regimes that in
aggregate achieve a desired population growth rate (e.g. 2%) target. All seven
management regimes can be mixed to create a large number of different conservation
scenarios, with different outcomes for the kiwi populations, and different costs.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page vii
Summary
Client and Project
Kiwis for kiwi (The Kiwi Trust, K4K) asked Landcare Research to estimate the likely
cost of achieving 2% population growth of all 10 accepted and perceived taxa of kiwi,
given that unmanaged populations are estimated to be declining at 2% per annum.
Due to limited availability of input data, this project estimates the cost of the additional
(to current) management required to halt declines or increase populations at 2% per
annum for only the kiwi taxa not already meeting these targets. It does not estimate the
total cost of achieving 2% population growth for all 10 kiwi taxa.
Objectives
To determine additional management so that all 10 kiwi taxa will a) stop declining, or
b) increase by 2% per annum.
To estimate the costs of this additional management.
Methods
For all 10 kiwi taxa, we first estimated the 2015 population size, and then allocated all
individuals to one of seven management regimes, each with its own estimated annual
population change rate. We then estimated the resultant, nett change rate after 1 year
and after 15 years for each taxon’s population, considering all regimes.
For each taxon failing to achieve 0% or 2% growth under current management, we then
modelled increasing the number of kiwi subject to predator management, until the nett
change rate achieved the 0% or 2% target.
To incorporate possible errors with model parameters, we repeated this modelling with
maximum and minimum values for the initial (2015) estimated population size, and low
and high (± 30%) population growth rates under the different regimes.
K4K invited community groups to report on management and equipment costs used in
the previous year at their sites, particularly for trapping. We also obtained costs for
important predator-control regimes such as aerial 1080 that community groups do not
use, and for ONE.
Aggregating these reported costs enabled us to estimate the total cost of current kiwi
management for communities, but not for DOC. We distinguished between funded and
volunteered time and equipment to assess the size of financial resources donated by
community groups to the kiwi recovery programme.
We estimated the annual cost of the additional management required to halt declines or
achieve 2% per annum growth compared with the direct cost of current management.
These estimates assume that existing DOC and community expenditures for kiwi
conservation remain at their current levels.
We also show the temporally weighted sum of the annual costs over a 15-year period,
i.e. the present value of these costs, using standard discounting practice and a 10%
discount rate (i.e., the temporal weighting factor).
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page viii Landcare Research
Results
Under current management for 15 years using most likely population model
parameters, five kiwi taxa (little spotted, Northland brown, Coromandel brown, rowi
and Haast tokoeka) are estimated to increase at mean annual rates that already exceed
2% per annum. Eastern and western browns will increase but at <2% per annum. The
remaining three taxa are estimated to decline at varying mean annual rates: 1.0% for
Fiordland tokoeka, 1.6% for great spotted and 1.8% for Rakiura tokoeka. Selecting low
or high growth rate parameters for modelling changes these outcomes and
classifications in negative and positive directions respectively.
Where kiwi taxa do not already meet 0% or 2% targets, putting unmanaged birds into
one of the six regimes of active management can halt the decline of all 10 taxa, and
with most likely model parameters can also increase all 10 by mean 2% per annum
for the next 15 years. These statements remain true even with low growth rates for all
taxa except great spotted and Fiordland, for which 2% increase may be unattainable.
The current, total, annual, community expenditure (funded and donated) is around $6.3
million for the five kiwi taxa with substantial community involvement (Northland,
Coromandel, eastern, western, great spotted). This excludes Fiordland and Rakiura
tokoeka, for which we have no community-generated data, as well as Haast tokoeka,
rowi and little spotted which are managed primarily by DOC.
From their reporting, we conclude that community groups currently donate 44% of their
total costs, with 59% donated in the Coromandel. A large share of the donated costs is
for time volunteered for administration, trap-checking and advocacy.
The additional annual cost of management required to achieve population stability for
the taxa currently not achieving this (eastern, great spotted, Fiordland, Rakiura) is $1.7
– 3.9 million, depending on population parameters chosen. Using most likely
parameters, the additional annual cost is $2.6 million. The present value of the total cost
over a 15-year period is $18 – $38.5 million, depending on the chosen parameters,
conservation scenario, and using a 10% discount rate. The additional 15-year costs
using most likely parameters have a present value of $27.5 million.
The additional annual cost of achieving 2% population growth for the taxa not already
achieving this (eastern, western, great spotted, Fiordland, Rakiura) is $2.6 – $11.3
million, depending on the model parameter choices and management scenarios. Using
most likely parameters, the additional annual cost is $8.1 million. The present value of
these costs over a 15-year period is $22.5 – $102 million, depending on the chosen
modelling parameters, conservation scenario, and using a 10% discount rate. The
additional 15-year costs using most likely parameters have a present value of $73.5
million.
Conclusions
Significant additional funding is required to achieve either of the conservation targets.
With the scenarios we used, and assuming most likely model parameter choices,
on average funding of $2.6 million annually on top of current (2014/2015) funding
is needed for the next 15 years to halt kiwi declines. To achieve 2% growth of all
10 taxa, additional funding of $8.1 million annually is needed for the same period.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page ix
Table Additional annual cost to achieve population stability or 2% growth for all 10 kiwi taxa, using most likely
population modelling parameters
Kiwi taxon Additional annual cost to achieve population stability
Additional annual cost to achieve 2% growth
Northland $0 $0
Coromandel $0 $0
Little spotted $0 $0
Haast $0 $0
Rowi $0 $0
Western (trapping scenario) $0 $90,000
Eastern (trapping scenario) $0 $322,000
Great spotted $1,500,000 $4,200,000
Fiordland $847,000 $2,900,000
Rakiura $250,000 $607,000
TOTAL $2,597,000 $8,119,000
The recently-announced funding package for kiwi conservation in Budget 2015 has an
injection of $11.2 million over the next 4 years. In the fourth year and thereafter, $6.8
million per annum will be available, which should allow stable populations to be
achieved. There would then be a shortfall of $1.3 million per annum to achieve 2%
growth across the board.
The investment commitment (present value) of the additional conservation effort
needed over a 15-year period to achieve kiwi population stability or 2% growth is
significant. As long as stoats and other threats to kiwi exist in significant numbers,
these costs will continue indefinitely. This suggests that research into more (cost)
effective predator control is likely to be a worthwhile investment.
Improved knowledge of sizes of current populations and their growth rates under
different management regimes for all 10 taxa, as well as improved quality of
community and other reported cost data on which this report rests, is required to refine
the predictions of this preliminary modelling. K4K and DOC both have roles to play in
developing improved technology and data, and in creating the conditions for these to be
shared and adopted by all kiwi conservation initiatives.
Landcare Research Page 1
1 Introduction
Kiwi collectively are an endemic bird family (Apterygidae) whose members were once found
throughout the main and large offshore islands of New Zealand, “probably originally in all
vegetated habitats” (OSNZ 2010). Currently there are 10 ‘kinds’ (actual or perceived taxa) of
kiwi, that in this report we refer to as ‘taxa’. Kiwi are taonga, and nationally iconic, birds.
New Zealanders perhaps connect more with kiwi than any other native animal because as
New Zealand nationals we call ourselves ‘kiwis’. However our small, flightless, feathered
namesakes have been struggling since various pest mammals were released, by design or by
mistake, into their environment. Predation of chicks and adults by stoats, ferrets, dogs and
cats has set kiwi populations throughout New Zealand on paths toward extinction.
By 2008, only ca 73 000 kiwi were best-guessed to remain, and unmanaged populations on
the mainland were estimated to be declining at 2–3% per annum (Holzapfel et al. 2008).
Currently, nine mainland kiwi taxa are deemed ‘threatened’ while the tenth – little spotted –
is recovering but only on pest-free offshore islands and in fenced mainland sanctuaries,
having been extirpated from its entire former mainland range (Robertson et al. 2013). It is not
just kiwi, moreover, that are at risk; other birds like kākā, kōkako, kākāriki, mōhua, whio,
kererū and kaki, as well as endemic lizards, frogs, invertebrates and freshwater fish are
declining due to predation and habitat destruction, disruption or pollution (Brown et al.
2015).
Past phases and outcomes of kiwi recovery management are described by Holzapfel et al.
(2008). The first kiwi recovery plan was published by the Department of Conservation in
1991 (Butler & McLennan 1991) and in the subsequent 24 years there has been enormous
progress with clarifying the taxonomic and trend status of populations, determining key
causes of decline, refining restoration tools; and enlisting the interest and involvement of
diverse community, corporate and government groups with kiwi conservation (Holzapfel et
al. 2008; Robertson & de Monchy 2012), although substantial uncertainties remain.
Major recovery tools have been: a) stoat- and other predator-trapping and poisoning at
various scales, including in ‘kiwi sanctuaries’; b) so-named ‘Operation Nest Egg’ (ONE) by
which eggs or chicks are removed from the wild and raised elsewhere until they can be
returned to the wild at a safe weight; and c) marooning populations on predator-free islands
and mainland ‘kohanga’ (nest or nursery). Most of these efforts have been and remain
successful in conserving kiwi populations at small (to ca 10 000 ha) and accessible sites
(Holzapfel et al. 2008; Robertson & de Monchy 2012). In the last 15 years, population
declines have been reversed for the rarest kiwi taxa, and reduced for others. The majority of
kiwi do not enjoy such intensive protection, however, and without pest management, many
populations continue to decline.
This report estimates the costs of the additional effort required to a) halt the decline of, or b)
increase by 2% per annum, all 10 actual or perceived kiwi taxa. This estimate will help guide
the strategy of Kiwis for kiwi (the Kiwi Trust; the key community partner of the kiwi
recovery programme) regarding how much money may need to be raised, and how and where
that funding should be invested.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 2 Landcare Research
2 Background
In November 2014, Kiwis for kiwi (hereafter K4K) commissioned Landcare Research
economist Florian Eppink to estimate the cost of changing an estimated 2% p.a. decline in
unmanaged kiwi nationwide into a 2% increase, so K4K could plan effective funding
strategies for achieving this goal. The original target deadline of early 2015 was changed to
late 2014 in order to support a Department of Conservation (hereafter DOC) and K4K bid to
Treasury for funding in the 2015 government budget. The bid was successful, although it did
not rely heavily on the Landcare Research analysis. The opportunity has since been taken to
strengthen technical data about kiwi populations and likely responses to management in a
revised report. These revisions include new kiwi population management scenarios and
underlying population modelling parameters developed by ecologists John Innes (Landcare
Research) and Hugh Robertson (DOC). Florian Eppink then estimated the cost of the new
scenarios to meet K4K’s original request. Unless otherwise credited, expert kiwi knowledge
in this report has come from Hugh Robertson, who has in turn derived information from
unpublished studies, knowledge, and sometimes opinions from many contributors to kiwi
recovery and its science.
3 Objectives
To determine additional management so that all 10 kiwi taxa will a) stop declining, or
b) increase by 2% per annum.
To estimate the costs of this additional management.
4 Modelling kiwi recovery strategies
4.1 Overview
Spanning two disciplines (in this case, ecology and economics) is never easy and this report
is no exception. We have tried to make both parts of the work understandable for all readers,
but the project is intrinsically complex. There are 10 kiwi taxa, whose populations are
subject in varying proportions to seven management regimes. We first modelled total
population growth rates using most likely numbers as well as other estimates above and
below them (e.g. low growth rate and high growth rate parameter choices). When we did
this, we discovered that some taxa were already meeting the population targets (either ‘no
decline’ i.e. 0% growth, or 2% growth), and so we did little further work with them. For just
the taxa that are not meeting our targets, we then modelled applying management to more and
more individuals in each population until annual growth rates reached the 0% or 2% targets.
Lots of different combinations of management regimes (that make up a conservation
scenario) could be applied, but we present just one or two conservation scenarios per taxon
(singular of ‘taxa’). We explain all of these terms in Appendix 1.
For each taxon of kiwi, we first estimated the 2015 population size, then allocated all
individuals to one of seven management regimes, each with its own estimated annual
population change rate. We then calculated the resultant nett change rate after 1 year and 15
years for each total population, considering all regimes applied.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 3
The management regimes were: ‘Operation Nest Egg’ (ONE); ‘kohanga’ or island marooning
or ‘kiwi farming’; sustained predator trapping preferably with poisoning every 5–7 years;
aerial poisoning of predators every 3 years; captive breeding (eastern browns only); 1080 in
bait bags to control predators (Rakiura tokoeka only); and ‘do nothing’.
4.2 Kiwi taxa and estimated 2015 population sizes
There are uncertainties about both kiwi taxonomy and kiwi population sizes (Table 1), whose
future resolution will assist recovery planning.
Molecular studies have revealed that both North and South Island brown kiwi have regionally
subdivided population structures that Baker et al. (1995) referred to as ‘cryptic species’.
Burbidge et al. (2003) and Baker & Burbidge (unpub. data) analysed mitochondrial DNA and
suggested that there were four genetically and regionally distinct kinds of North Island brown
kiwi, in Northland, Coromandel and eastern (mainly Hawkes Bay, Bay of Plenty, East Cape)
and western (mainly Taranaki/Wanganui) North Island. These currently are aggregated as
Apteryx mantelli and share a threat status, and until their taxonomy resolves further will by
precautionary principle be managed separately (Herbert & Daugherty 2002; Holzapfel et al.
2008). Scientifically, the currently accepted 10 kinds of kiwi could be referred to as ‘known
or suspected recognisable taxonomic units’ but this is cumbersome. In this report, to avoid
confusion, we refer to the currently accepted 10 kinds of kiwi as ‘taxa’, even though
several do not have formal taxonomic description. We frequently refer to them by their
common name, e.g. ‘Coromandel and rowi’, but generally drop the words ‘kiwi’ and
‘tokoeka’ from these references simply to avoid repetition.
We estimated 2015 population sizes by taking published best guesses in Holzapfel (2008) and
calculating what these populations would have become 7 years later, by allocating the 2008
birds to either managed or unmanaged regimes. These regimes were assumed to result in
different growth rates – a 1–15% increase if managed and a 2–3% decline if unmanaged. To
acknowledge uncertainty in these 2015 population estimates, we also suggest maximum and
minimum error sizes in them: 10% for little spotted and rowi; 20% for Coromandel and
Haast; and 30% for all others. The increasing error margins reflect how well each population
is known, due to varying efforts of previous research and census, varying remoteness in New
Zealand, and the very different total areas (hectares) of each kiwi.
Area (ha) occupied by each taxon was determined by GIS calculations undertaken by DOC
staff. These calculations exclude areas where the population is extremely sparse and non-
viable.
We did not consider the management of populations that are, or could be, artificial hybrids
between different kiwi taxa (i.e. Ponui Island, Pukaha Mt Bruce, Rimutaka, and possibly
Hauturu/Little Barrier Island). Their management will contribute to species-level goals, but
not the taxon-specific goals considered in this report.
Page 4
Table 1 Common and scientific names (OSNZ 2010), current NZ threat status, main criterion and explanatory qualifiers (Robertson et al. 2013), 2015 population size (most
likely, minimum, maximum), and estimated area occupied (H. Robertson pers. comm.) of all 10 kiwi taxa recognised in the Kiwi Recovery Plan 2008 – 2018 (Holzapfel et al.
2008). The mean density data in column 7 are derived by dividing the most likely 2015 population size (column 6) by the area occupied (column 7). Status qualifiers are: CD
conservation dependent, DE designated, DP data poor, Inc increasing, OL one location, PD partial decline, RF recruitment failure, RR range restricted
Common name Region Scientific name Current threat status Status criterion and qualifiers Population size 2015
Area (ha) occupied (mean density) 2015
Little spotted kiwi Apteryx owenii Recovering 1–5000 mature individuals.
CD, Inc, RR 1800
(1620–1980)
5600
(0.321/ha)
Great spotted kiwi A. haastii Threatened (nationally
vulnerable) 5–20 000 mature individ. 30–70% decline DP, RF
14 800
(10 360–19 240)
800 000
(0.019/ha)
North Island brown kiwi
Northland A. mantelli
Threatened (nationally vulnerable)
5–20 000 mature individ. 30–70% decline CD, PD, RF
8,200
(5740–10 660)
700 000
(0.012/ha)
Coromandel A. mantelli 1700
(1360–2040)
125 000
(0.014/ha)
Eastern A. mantelli 7150
(5005–9295)
1 400 000
(0.005/ha)
Western A. mantelli 7500
(5250–9750)
860 000
(0.009/ha)
Rowi (Okarito brown kiwi)
A. rowi Threatened (nationally critical)
<250 mature individuals CD, inc., OL, RF
500
(450–550)
15 000
(0.033/ha)
Tokoeka (southern brown kiwi)
Haast Apteryx australis australis
Threatened (nationally critical)
<250 mature individuals CD, inc., OL, RF
400
(360–440)
30 000
(0.013/ha)
Rakiura (Stewart Is.) Apteryx australis lawryi
Threatened (nationally endangered)
Moderate population, ongoing decline DE, DP, OL, RF
13 000
(9100–16 900)
151 100
(0.086/ha)
Fiordland Apteryx australis australis
Threatened (nationally vulnerable)
5–20 000 mature individ. 30–70% decline PD, RF
12 500
(8750–16 250)
800 000
(0.016/ha)
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 5
Kiwi distribution is approximated in Figure 1.
Figure 1. Spatial distribution of kiwi in New Zealand. North Island brown kiwi are managed as Northland,
Coromandel, eastern and western populations, while South Island tokoeka have three regional populations in
Haast, Fiordland and Rakiura (Stewart Island). Source: Kiwis for kiwi
4.3 Current kiwi threats and management regimes, and resultant estimated population growth rates
4.3.1 Threats and management regimes
Predation by pest mammals, particularly stoats (Mustela erminea) but also ferrets (Mustela
furo), dogs (Canis familiaris), and cats (Felis catus), is considered the key cause of current
kiwi declines (McLennan et al. 1996; Robertson et al. 2011). Other threats include loss of
genetic diversity and other localised events such as vehicle strikes, fire, disease, and ongoing
habitat loss (Holzapfel et al. 2008) but overcoming predation is undoubtedly the most
effective way to ameliorate these less important issues.
There are currently four major and two minor active management regimes for kiwi
(Holzapfel et al. 2008; Robertson & de Monchy 2012), and a seventh inactive one to which
most (76%, Table 2) kiwi are subjected – no pest management. The four major active regimes
combat mammalian predation in some way. They are:
Operation Nest Egg (ONE; Colbourne et al. 2005; Robertson et al. 2006; Gillies et al.
2013), in which eggs and young chicks are removed from predation and other risks in
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 6 Landcare Research
the wild, then returned as subadults that have smaller likelihood of predation. Currently
we estimate that ca 540 kiwi of seven taxa are subject to ONE (Table 2).
Kohanga, marooning, or ‘kiwi farms’ in which populations are established on pest-free
islands or fenced sanctuaries, and birds are later harvested for translocation to
strengthen kiwi populations elsewhere. Little spotted kiwi are managed entirely in this
way (Ramstad et al. 2013). Currently we estimate that ca 2750 kiwi of nine taxa are
subject to kohanga (Table 2).
Trapping, preferably with episodic use of toxin every 5–7 years. Traps (DOC 200s,
DOC 250s, and others) are used to target stoats, ferrets, and cats on large scales,
particularly in DOC Kiwi Sanctuaries where trapping blocks average around 12 000 ha
(Robertson & de Monchy 2012). The occasional use of toxins that have a secondary
poisoning effect can eliminate resident, untrappable stoats. Currently, we estimate that
ca 8580 kiwi of eight taxa are protected by trapping (Table 2).
Aerial 1080 poisoning every 3–7 years. The broad-spectrum poison 1080 is aerially
applied to very large areas of New Zealand forest each year to target possums
(Trichosurus vulpecula) and ship rats (Rattus rattus) for conservation and disease
prevention objectives (Parliamentary Commissioner for the Environment 2011) but
with known secondary poisoning for stoats, ferrets, and cats. The frequency of
operations varies, also depending on objectives (Brown & Urlich 2005). Currently we
estimate that ca 3780 kiwi of eight taxa are protected by regular aerial 1080 operations
(Table 2). The recent landscape-scale use of aerial 1080 in the ‘Battle for our Birds’, in
response to an exceptionally widespread seeding of beech (Fuscospora and Lophozonia
spp.) trees and predicted resultant high numbers of rodents and stoats, will have
benefitted some kiwi populations for the first time. One-off aerial distribution of
brodifacoum is also used, to achieve eradications of mammal pests on islands and
fenced mainland sanctuaries only.
The offspring of 100 adult eastern browns held in captivity are also factored in for that taxon
only, and on Stewart Island, pest control has used ground-based poisoning methods rather
than aerial operations (Table 2).
In areas close to human communities or in remote areas where pigs are hunted, dogs are
significant threats to adult kiwi, especially in Northland (Robertson et al. 2011). Kiwi-
aversion training for dogs is a possible instrument to reduce kiwi mortality, but training needs
to be repeated at least every year (Dale et al. 2013) and its effectiveness has been questioned
(Jones 2006; R. Colbourne, Department of Conservation, pers. comm.). We accept that
aversion training may have value for kiwi recovery, but it has not been included as a
management regime in this analysis because of uncertainty about its effectiveness, and the
absence of data about population growth rates with and without it.
4.3.2 Current population growth rates
To enable us to model the outcomes of taking different management options, we allocated all
kiwi in each of the 2015 populations to a current management regime, for each of which we
estimated a particular resultant growth rate (finite rates of increase that may be >1 for
increasing populations or <1 for declining populations; Table 2). In this report we also
present growth rates as say ‘2% per annum’ because of its popular use. For example, a
2% increase, is simply a growth rate of 1.02, and a 2% decline is a growth rate of 0.98.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 7
We have used published data on population growth rates under different regimes where
available (Holzapfel et al. 2008; Robertson et al. 2011; Robertson & de Monchy 2012), but
most rates data in Table 2 derive from unpublished data or expert assessment by Hugh
Robertson about how published rates for one taxon may apply to another, and how rates may
have changed over time. Most of the rates we select here have not been directly measured in
the wild for each taxon. Addressing this shortfall is clearly desirable in the future.
Mean per annum rates that we used in modelling (Table 2) were derived as follows:
a) Little spotted. Fortuitously, little spotted kiwi were moved to Kāpiti Island in 1912
because they became extinct on the mainland during the 20th
century. From Kāpiti,
‘insurance’ populations have been established on a further seven predator-free islands
(Anchor Island, Chalky Island, Hen Island, Long Island, Motuihe Island, Tiritiri
Matangi, Red Mercury Island) and at two mainland sanctuaries (Cape Sanctuary and
Zealandia). Therefore, kohanga is the only regime that applies to this taxon.
Population growth rates measured on Long, Red Mercury, Hen and Tiritiri Matangi
Islands during 1992–97 averaged 7.25% p.a. (Colbourne & Robertson 1997) but we
selected a slightly lower rate (5% p.a., i.e. 1.05) because the growth rate will slow as
K (carrying capacity) is approached. The lower growth rate (1.02) given to Kapiti
(which is at K) matches the ca 25 individuals that are harvested from there annually to
start new sites.
b) Great spotted. We gave ONE a smaller growth rate (1.03) than for North Island
browns or rowi because it has proven less successful. The trapping rate (1.02) is
derived from mean growth rates of kiwi calls of +1.7% p.a. at three stations in the
south Hurunui (trapping with some ground toxins). The 1080 rate (1.003) is based on
call counts increasing at 8 listening stations under intermittent aerial 1080 at Gouland
Downs (5 stations) and Heaphy (3 stations). A ‘do nothing’ growth rate of 0.98 (i.e. a
decline) reflects an overall 1.97% p.a. decline in call rates at 10 unmanaged listening
stations in Westport coal measures (4), the Taramakau (3), and North Hurunui (3)
over 17–18 years since the mid-1990s, and a mean 1.6% p.a. decline in the number of
territories in 2000 ha of the northern Hurunui during 2000–2015 (Robertson et al.
unpub. data).
c) Northland. ONE in Northland resulted in a mean growth rate of 1.125 (Robertson et
al. 2011). The kohanga rate (1.10) derives from the number of birds that have been
removed from Motuora and Matakohe Islands over ca 12 years. The trapping rate
(1.06) is derived from Northland sanctuary data (8.6 % p.a. increase, Robertson & de
Monchy, 2012) but is slightly smaller to account for trap-shy stoats arising from
continuous trapping, as well as unsustainable trap-checking and baiting practices. The
1080 rate (1.02; Waipoua Forest only) is derived as per western (below). The ‘do
nothing’ rate (0.97) is from Robertson et al. (2011) and Holzapfel et al. (2008).
d) Coromandel. As with Northland, except while original growth from trapping was
observed to be 11.3% p.a. (Robertson & de Monchy 2012), chick survival declined in
the last few years when kiwi were monitored closely.
e) Eastern. ONE, trapping, aerial 1080 and ‘do nothing’ rates are all as per Northland,
although ferrets are more important than dogs as decline factors. The c.15 sites that
hold ca100 easterns in captivity release a surplus of ca 5 birds per year, hence an
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 8 Landcare Research
additive 1.05 growth rate from that regime. The 100 adults allocated to a kohanga are
all at Cape Sanctuary (Cape Kidnappers) and reflect likely numbers in the very near
future.
f) Western. The ONE programme at Tongariro had high hatching success and chick and
subadult survival, resulting in a high growth rate (1.15) from these birds (Robertson &
de Monchy 2012). The 1080 rate (1.02) is based on a 14-year mostly unpublished
study at Tongariro Forest that has monitored brown kiwi productivity through 5-
yearly aerial 1080 operations (Robertson & de Monchy 2012; J. Guillotel, H.
Robertson, N. Sutton, DOC, unpub. data). Other rates are derived as per Northland.
g) Rowi. Rowi rates are derived as per western, except that aerial 1080 is given a smaller
rate (1.01) because unpublished data suggest the rowi response to these operations is
not as good. That may be because rowi chicks go to and from nests repeatedly and so
may be found more readily by stoats. We used 1.15 for ONE for rowi rather than
1.094 as in Robertson and de Monchy (2012), because ONE management for this
species has improved greatly since the early 2000s.
h) Haast. Mean annual growth under ONE was measured at 7.1% p.a. by Robertson and
de Monchy (2012) but Hugh Robertson considers that 5% p.a. growth (rate 1.05) is
likely to be more accurate now. The kohanga rate of 1.10 is based on other kiwi taxa
in predator-free sites; of kohanga sites with Haast tokoeka, Coal Island (1189 ha) has
abundant room for population growth, while Raratoka (86 ha) and Orokonui Eco-
sanctuary (307 ha) are much smaller and will reach K sooner. The rate under stoat
trapping is known to be low (1.03) because intermittent beech (Fuscospora and
Lophozonia spp.) masts resulted in numerous stoats that killed many radio-tagged
chicks, despite trapping (Robertson & de Monchy 2012). The predicted growth rate if
nothing is done is 0.97, a decline (Holzapfel et al. 2008).
i) Fiordland. Growth rates are predicted to be low (1.05) for Fiordland kohanga kiwi
because these very southern sites (Secretary and Resolution Islands, 45–46° S) may
have intrinsically low productivity, Secretary is intermittently colonised by stoats,
Resolution has mice (Mus musculus) that may compete with kiwi for invertebrate
prey, and access to both islands to harvest kiwi is comparatively difficult. Rates for
trapping and ‘do nothing’ regimes were measured in the field and are from Tansell,
Edmonds and Robertson, Department of Conservation, unpub. data. The population
change rate under aerial 1080 (1.02) is from the long-term, measured result for
westerns at Tongariro Forest (see above).
j) Rakiura. Our suggested growth rate for Rakiura tokoeka in kohanga (1.10) is higher
than for Fiordland tokoeka because the sites (Ulva Island and Dancing Star sanctuary)
are small (270 ha and 160 ha respectively) and readily accessed to harvest birds.
There are no mustelids on Rakiura and so only feral cats are targeted by trapping. The
suggested growth rates of 1.04 under this regime, and for ground-based poisoning, are
simply best guesses. The 0.98 growth rate (2% per annum decline) is from Holzapfel
et al. (2008), and from mapping territories at Masons Bay using trained dogs and
radio transmitters on birds in a 125 ha area during 1993–2013 (R. Colbourne, H.
Robertson, DOC, unpub. data).
Page 9
Table 2 ‘Best estimate’ (and min.-max.) current numbers of all 10 kiwi taxa that are subject to different management regimes, and the mean per annum population growth
rates that apply to each (see 4.2.2 for derivations). Rounded, best estimate, min. and max. population sizes after one and 15 years derived from ‘best estimate’ current rates
are also shown, as are mean, whole-population, per annum growth rates after 1 and 15 years
Regime No. kiwi in each regime Current p.a. growth rate per regime
Population size after… Mean, nett, p.a. growth rate after… 1 year 15 yrs 1 year 15 years
Little spotted
Kohanga (all but Kapiti) 600 1.05 1.030 1.032
Kohanga (Kapiti) 1200 1.02 TOTAL 1800 1852 2867
MIN-MAX 1620–1980 1669–2039 2527–3088
Great spotted
ONE 8 1.03
0.983 0.984 Trapping w. 5–7 yr toxin 350 1.02 1080 each 5–7 years 1500 1.003 Do nothing 12942 0.98
TOTAL 14800 14 592 12 428 MIN-MAX 10 360–19 240 10 202–18 904 9762–14 889
Northland
ONE 40 1.125
1.015 1.028 Kohanga 60 1.1 Trapping w. 5–7 yr toxin 3900 1.06 1080 each 3 years 75 1.02 Do nothing 4125 0.97
TOTAL 8200 8323 12 325 MIN-MAX 5740–10 660 5828–10 818 8654–15 995
Coromandel
ONE 50 1.125
1.040 1.048 Kohanga 40 1.1 Trapping w. 5–7 yr toxin 1180 1.06 Do nothing 430 0.97
TOTAL 1700 1768 3411 MIN-MAX 1080–1620 1417–2119 2780–4043
Eastern
ONE 100 1.125
0.99 1.001
Captive release 100 1.05 Kohanga 100 1.05 Trapping w. 5-7 yr toxin 1150 1.06 1080 each 3 years 50 1.02 Do nothing 5650 0.97
TOTAL 7150 7078 7281 MIN-MAX 5005–9295 4957–9199 5131–9432
Page 10
Regime No. kiwi in each regime Current p.a. growth rate per regime
Population size after… Mean, nett, p.a. growth rate after… 1 year 15 yrs 1 year 15 years
Western
ONE 100 1.15
1.002 1.013 Kohanga 130 1.1 Trapping w. 5–7 yr toxin 1350 1.06 1080 each 3 years 1700 1.02 Do nothing 4220 0.97
TOTAL 7500 7516 9064 MIN-MAX 5250–9750 5267–9766 6423–11 704
Rowi
ONE 120 1.15 1.047 1.039 Kohanga 20 1.1
1080 each 3 years 360 1.01 TOTAL 500 524 891
MIN-MAX 450–550 473–574 833–950
Haast
ONE 120 1.05
1.037 1.042 Kohanga 60 1.1 Trapping w. 5–7 yr toxin 140 1.03 Do nothing 80 0.98
TOTAL 400 415 738 MIN-MAX 360–440 374–455 676–799
Fiordland
Kohanga 500 1.05
0.988 0.99 Trapping w. 5–7 yr toxin 500 1.012 1080 each 3 years 100 1.02 Do nothing 11400 0.984
TOTAL 12500 12 351 10 722 MIN-MAX 8750–16 250 8645–16 056 7506–13 939
Rakiura
Kohanga 40 1.1
0.981 0.982 Trapping w. 5–7 yr toxin 10 1.04 Toxin in bait stations 200 1.04 Do nothing 12 750 0.98
TOTAL 13 000 12 757 9962 MIN-MAX 9100–16 900 8930–16 579 6977–12 842
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 11
In total, 24% of the estimated 68 000 remaining kiwi (all 10 taxa) are under some
management, and the remaining majority (76%) are unmanaged. However, the proportion of
each taxon’s population that is under management varies greatly, from 2% for Rakiura
tokoeka to 100% for little spotted kiwi.
Across all kiwi taxa, there is an inverse relationship between total population size and the
proportion of each population that is pest-managed (Fig. 2).
Figure 2. Relationship between total population size and % of each population that is pest-managed, for all 10
kiwi taxa.
4.3.3 Modelling 15-year outcomes at current sites
We modelled population size and mean annual growth rates of all 10 kiwi taxa within 1-year
and 15-year horizons by assuming that:
a) the same places and areas (hectares) are managed for the whole 15 years
b) new birds produced under each regime recruit within the managed area and do not
disperse outside it
c) there are no K effects on population size within the 15-year period
d) management effectiveness (pest control efficacy, and kiwi demographic responses to
it) remain the same from year to year.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 12 Landcare Research
We selected 15 years because it is sufficient time for differences between combinations of
regimes to become apparent, yet is short enough to drive planning decisions now.
Whole population growth rates can change a little in 15 years because the numbers of kiwi
within the managed areas grow cumulatively, while those within unmanaged areas slowly
decline, so that different numbers and proportions of kiwi are subject to each regime as time
passes. Kiwi will eventually disappear entirely from unmanaged places and remain only in
pest-managed ones if such scenarios persist, as is the case already for other more pest-
sensitive birds such as kokako (Callaeas wilsoni) and saddleback (Philesturnus
carunculatus).
Under current management (status quo) for 15 years using most likely population growth
rates, five taxa (little spotted, Northland brown, Coromandel brown, rowi and Haast tokoeka)
are estimated to increase at mean annual rates that already exceed 2% per annum. Eastern
and western browns will increase but at <2% per annum. The remaining three taxa are
estimated to decline at varying mean annual rates: 1.0% p.a. for Fiordland tokoeka, 1.6% p.a.
for great spotted and 1.8% p.a. for Rakiura tokoeka (Tables 2, 3).
Selecting low or high growth rate parameters changes these outcomes and classifications in
negative and positive directions respectively (Table 3). Compared with best estimate growth
rates, in 15 years with low (best estimate minus 30%) rates of growth, Northland slips from
increasing at >2% p.a. to increasing at <2% p.a., while easterns change from increasing to
declining. With high (best estimate plus 30%) rates, western browns are boosted from
increasing at less than 2% p.a. to increasing at more than 2% p.a. (Table 3).
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 13
Table 3 Effects of varying population growth rates (best estimate, ±30%) under the various management
regimes (section 4.2.2) on current and modelled future (rounded 1 year, 15 years) population size and mean, per
annum, total-population growth rate for all 10 kiwi taxa.
Taxon Best estimate growth rates Low growth rates (–30%)
High growth rates (+30%)
Current 1 year 15 yrs 1 year 15 yrs 1 year 15 yrs
Little spotted Population 1800 1854 2867 1838 2457 1870 3211
Total rate 1.030 1.032 1.021 1.021 1.039 1.039
Great spotted Population 14800 14 553 11 610 14 472 10 707 14 635 12 599
Total rate 0.983 0.984 0.978 0.979 0.989 0.989
Northland Population 8200 8323 12 325 8212 9808 8434 15 457
Total rate 1.015 1.028 1.001 1.012 1.029 1.043
Coromandel Population 1700 1768 3411 1740 2650 1796 4375
Total rate 1.04 1.048 1.024 1.03 1.057 1.065
Eastern Population 7150 7078 7281 6998 5694 7158 8898
Total rate 0.990 1.001 0.979 0.988 1.001 1.015
Western Population 7500 7516 9064 7436 7536 7597 10 938
Total rate 1.002 1.013 0.991 1.000 1.013 1.025
Rowi Population 500 524 891 517 764 531 1033
Total rate 1.047 1.039 1.033 1.029 1.061 1.050
Haast Population 400 415 738 409 594 420 926
Total rate 1.037 1.042 1.023 1.027 1.050 1.058
Fiordland Population 12 500 12 351 10 722 12 286 9845 12 415 11 691
Total rate 0.988 0.990 0.983 0.984 0.993 0.996
Rakiura Population 13 000 12 757 9962 12 677 9016 12 838 11 019
Total rate 0.981 0.982 0.975 0.976 0.988 0.989
We estimate that if current management is maintained at all sites for 15 years, then there
would be for all 10 kiwi taxa combined a decline of 0.1% per annum. That is, current
management is close to holding the national kiwi population stable. However, declines in a
few, currently more abundant taxa (Rakiura, Fiordland, great spotted) roughly equate to
increases in more but smaller population taxa (Coromandel, Haast, rowi, little spotted,
Northland, western).
We also estimate that if all management ceased, but assuming that island biosecurity
continued so that there were no pest invasions to islands, there would be a national all-kiwi-
taxa decline of 2.0 % per annum, as already widely publicised.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 14 Landcare Research
4.4 Modelling halting the decline and achieving 2% per annum growth
For each taxon failing to achieve 0% p.a. or 2% p.a. growth under current management, we
then modelled increasing the number of kiwi subject to active management using our
opinions about the most practicable and acceptable management regimes in each case, until
the whole population change rate achieved the mean 0% p.a. or 2% p.a. target over 15 years.
Other combinations of numbers of birds subject to different management are possible, and
may reach the desired targets, but at different costs to those estimated here.
We repeated this modelling for each taxon with estimated maximum and minimum values for
the initial (2015) population size and estimated low and high (± 30%) population growth rates
under the different regimes, some results of which we report here.
4.4.1 Halting the decline
‘Halting the decline’ means achieving at least 0% population growth per annum over the
modelled 15-year period; that is, the population in 2030 will be the same as it is in 2015.
With most likely growth rate parameters from the various management regimes (section
4.2.2), populations of all taxa except great spotted, Fiordland, and Rakiura, will have grown
in 15 years at the current rate of investment in their recovery. With low growth rate
parameters used in the modelling, eastern browns also fail to achieve growth (Table 3).
In our suggested scenarios, subjecting extra kiwi to aerial 1080, trapping or kohanga regimes
halts the decline of great spotted, eastern brown, and Fiordland populations, while on Rakiura
this is achieved by increasing use of ground-poisoning (Table 4).
Page 15
Table 4 Possible conservation scenarios of allocating kiwi to different management regimes that achieve 0% p.a. growth (i.e. halt the decline). Only taxa and situations that
required re-allocation of birds between management regimes to achieve 0% p.a. growth are shown. Figures in bold and italics show the total numbers needed under that
management regime (removed from the do-nothing category) to halt the decline. Figures in brackets for eastern browns under the low growth rate parameters show an
example, alternative, allocation scenario using trapping rather than aerial 1080 that also halts decline
‘Kind' of kiwi Regime No. kiwi allocated to each regime Current best estimate population
Revised best estimate population
Minimum pop. (–30%)
Maximum pop. (+30%)
Low growth rates (–30%)
High growth rates (+30%)
Great spotted
ONE 8 8 8 8 8 8 Trapping w. 5–7 yr toxin 350 350 350 350 350 350 1080 each 5–7 years 1500 11 878 8101 15 654 12 921 10 278 Do nothing 12 942 2564 1901 3228 1521 4164
2015 TOTAL 14 800 14 800 10 360 19 240 14 800 14 800 MEAN 15-YR RATE 0.984 1.0 1.0 1.0 1.0 1.0
Eastern
ONE 100 100 (100) Captive release 100 100 (100) Kohanga 100 100 (100) Trapping w. 5–7 yr toxin 1150 1150 (2060) 1080 each 3 years 50 1792 (50) Do nothing 5650 3908 (4740)
TOTAL 7150 7150 MEAN 15-YR RATE 1.001 1.0
Fiordland
Kohanga 500 500 350 650 500 500 Trapping w. 5–7 yr toxin 500 500 350 650 500 500 1080 each 3 years 100 3271 2290 4252 5385 1394 Do nothing 11 400 8229 5760 10 698 6115 10 106
2015 TOTAL 12 500 12 500 8750 16 250 12 500 12 500 MEAN 15-YR RATE 0.990 1.0 1.0 1.0 1.0 1.0
Rakiura
Kohanga 40 40 40 40 40 40 Trapping w. 5–7 yr toxin 10 10 10 10 10 10 Toxin in bait stations 200 3060 2100 4020 4945 1690 Do nothing 12 750 9890 6950 12 830 8005 11 260
TOTAL 13 000 13 000 9100 16 900 13 000 13 000 MEAN 15-YR RATE 0.982 1.0 1.0 1.0 1.0 1.0
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 16 Landcare Research
4.4.2 Achieving 2% growth p.a.
Five of the 10 kinds of kiwi (little spotted, Northland, Coromandel, rowi, and Haast) are
already estimated to be increasing at 2% per annum with most likely growth rate parameters
under the various management regimes (section 4.2.2). With low growth rate parameters,
Northland brown kiwi slip below 2% p.a. increase. With high growth rate parameters, only
the most struggling populations – great spotted, eastern, Fiordland and Rakiura – still fail to
achieve 2% growth p.a. (Table 3).
Achieving mean annual growth of 2% p.a. over 15 years is substantially more demanding
than just halting the decline. In our suggested scenarios, substantially more trapping and/or
aerial 1080 can eventually achieve 2% growth p.a.for great spotted, Northland, eastern and
western kiwi, although with low growth input rates, 96% of each of the great spotted and
eastern populations have to be managed to do so (Table 5). With low growth rate parameters,
on Rakiura 80% (10 350/13000) of all tokoeka may have to be under protection by trapping
and ground-poisoning to maintain this as a mean annual growth over 15 years.
For Northland and Coromandel populations we manipulated the number of kiwi subject to
trapping rather than aerial 1080 because of the availability of community labour and likely
opposition to aerial 1080.
For eastern brown kiwi, having 100 birds under a kohanga regime at Cape (Kidnappers)
Sanctuary is reasonable, but if this site could be built up rapidly to 300 kiwi by translocation
from unmanaged populations, then our scenarios could change. Adding 200 birds to kohanga
at Cape Sanctuary could relieve 1000 others from requiring aerial 1080 to achieve the same
outcome.
Our preliminary modelling suggests that for great spotted kiwi, increasing the frequency of
aerial 1080 from every 5–7 years to every 3 years, with a resultant growth rate change from
1.003 to 1.02, can achieve 2% p.a. gain with all parameter choices except that with low
growth rates. In that case, maximising the number of birds under trapping and aerial 1080
would achieves 15-year mean per annum rate of only 1.4% (Table 5).
Similarly, substantial increases in the amount of aerial 1080 poisoning used in Fiordland can
achieve a population increase of 2% per annum over 15 years with all parameter choices but
one. With low growth rate parameters, this may be unobtainable (Table 5), because ONE is
not likely to be an efficient option in such a large population in the remote and difficult
Fiordland landscape, where, unlike Haast, the population is widely scattered across the range,
kohanga space on islands is limited, and mean annual growth from aerial 1080 may be
unpredictable because of intermittent beech masts and high stoat numbers, or there could be a
lack of rodents to carry the toxin to stoats in intervening years. No monitoring of Fiordland
tokoeka populations through a 1080 operation has ever been carried out.
Page 17
Table 5 Possible conservation scenarios of allocating kiwi to different management regimes that achieve 2% p.a. growth. Only taxa and situations that required re-allocation
of birds between management regimes to achieve 2% growth p.a. are shown. Figures in bold and italics show the total numbers needed under that management regime
(removed from the do-nothing category) to achieve 2% p.a. growth. The highlighted cells for great spotted and Fiordland under low growth rates are the only cases where
manipulating regimes did not result in a 2% p.a. population gain. Figures in brackets for eastern and western browns under the low growth rate parameters show example,
alternative, allocation scenarios using trapping and kohanga rather than aerial 1080 that also cause 2% growth p.a.
Kiwi taxon Regime No. kiwi allocated to each regime Current best estimate population
Revised best estimate population
Minimum pop. (–30%)
Maximum pop. (+30%)
Low growth rates (–30%)
High growth rates (+30%)
Great spotted
ONE 8 8 8 8 8 8
Trapping w. 5–7 yr toxin 350 700 700 700 3200 700
1080 each 3 years (a change) 1500 14 091 9651 18 531 11 592 11 306
Do nothing 12942 1 1 1 0 2786
2015 TOTAL 14 800 14 800 10 360 19 240 14 800 14 800
MEAN 15-YR RATE 0.988 1.02 1.02 1.02 1.014 1.02
Northland
ONE 40 40
Kohanga 60 60
Trapping w. 5–7 yr toxin 3900 4843
1080 each 3 years 75 75
Do nothing 4125 3182
2015 TOTAL 8200 8200
MEAN 15-YR RATE 1.028 1.02
Eastern
ONE 100 100 70 130 100 (100) 100
Captive release 100 100 100 100 100 (100) 100
Kohanga 100 100 70 130 100 (300) 100
Trapping w. 5–7 yr toxin 1150 1150 805 1495 1150 (3603) 1150
1080 each 3 years 50 3336 2289 5749 5388 (50) 1058
Do nothing 5650 2364 1660 3005 312 (2997) 4642
2015 TOTAL 7150 7150 5005 10660 7150 7150
MEAN 15-YR RATE 1.001 1.02 1.02 1.02 1.02 1.02
Page 18
Kiwi taxon Regime No. kiwi allocated to each regime Current best estimate population
Revised best estimate population
Minimum pop. (–30%)
Maximum pop. (+30%)
Low growth rates (–30%)
High growth rates (+30%)
Western
ONE 100 100 100 100 100 (100)
Kohanga 130 130 91 169 130 (300)
Trapping w. 5–7 yr toxin 1350 1350 945 1755 1350 (3025)
1080 each 3 years 1700 3146 2092 4200 5455 (1700)
Do nothing 4220 2774 2022 3526 465 (2375)
2015 TOTAL 7500 7500 5250 9750 7500
MEAN 15-YR RATE 1.013 1.02 1.02 1.02 1.02
Rakiura
Kohanga 40 40 40 40 40 60
Trapping w. 5–7 yr toxin 10 10 10 2500 3000 10
Ground-based poisoning 200 7292 5063 7032 7310 4990
Do nothing 12750 5658 3987 7328 2650 7940
2015 TOTAL 13 000 13 000 9100 16 900 13 000 13 000
MEAN 15-YR RATE 0.982 1.02 1.02 1.02 1.02 1.02
Fiordland
Kohanga 500 500 350 650 700 500
Trapping w. 5–7 yr toxin 500 500 350 650 500 500
1080 each 3 years 100 10 980 7686 14 274 11 300 8310
Do nothing 11400 520 364 676 0 3190
2015 TOTAL 12 500 12 500 8750 16 250 12 500 12 500
MEAN 15-YR RATE 0.990 1.02 1.02 1.02 1.015 1.02
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 19
5 Estimating current and additional cost
Kiwi conservation involves predator control as well as a range of other supporting activities,
such as advocacy, and kiwi call monitoring. Our first analysis of the data K4K requested
from the kiwi conservation groups considered the proportion of community costs that are
volunteered or funded.
Our second analysis focuses on the costs of stabilising and increasing the populations of the
kiwi taxa that are not already achieving these targets (eastern, western, great spotted,
Fiordland, Rakiura), through additional management effort, for all of the population model
parameter options (most likely, high/low initial population, high/low growth rates). We
estimated these costs using data from the reporting provided by the kiwi conservation groups,
from published sources and DOC’s internal reporting systems.
We estimated the present value of the additional costs over 15 years with a 10% discount rate
in accordance with Treasury guidance.1 Discounting is an economic technique that accounts
for people tending to prefer having money now, rather than having a little more money later.
Discounting is an essential consideration when making decisions about long-term
investments, and the discount rate is a critical parameter. A low (cf. high) discount rate means
people weigh future costs more (cf. less) heavily in their decisions; thus the present value of
future costs will be higher (cf. lower). Therefore we also offer cost estimates at 5% and 15%
discount rates to illustrate the impact of time preferences that deviate from the Treasury
guidance.
5.1 Cost data considerations
The data provided by kiwi conservation groups at the request of K4K are critical for this
exercise.
The communities reported on a range of cost items, which we relate to costs based on
publicly available information as described in Appendix 2. This approach provides an
estimate for the costs communities incur under the current conservation scenario, and can be
used to estimate the additional costs of other conservation scenarios.
Due to decisions we made about whether to include or exclude certain costs (mainly fences)
and cyclic implementation of management regimes (mainly the 6-year cycle for predator
control using poisons), there will inevitably be discrepancies between our cost estimates
based on community reporting and our suggested management regimes and conservation
scenarios. Our cost estimates should be considered as preliminary.
Data sources of note are Gillies et al. (2013) for cost estimates per ONE juvenile released
(although the quality of their data also relied heavily on interpretation of queries made to
1 http://www.treasury.govt.nz/publications/guidance/planning/costbenefitanalysis/primer/15.htm (Accessed
February 23rd, 2015)
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 20 Landcare Research
users), PCE (2013), and DOC’s experience of the costs per hectare of aerial poisoning
operations. For several cost items, particularly trapping equipment, we found vendor prices
and applied sensitivity analysis to them. This provided an error range that proved to be
insignificant compared with the total costs; therefore the average of the error range was used
for the cost estimates.
The level of reporting about different kiwi taxa inevitably reflected the number of community
conservation groups actively managing each of them. For Northland brown, for instance, we
have many reports. This suggests that the averages of cost items are a good reflection of the
actual costs for Northland brown. The number of community groups reporting on the other
kiwi was (much) smaller, and the costs of management regimes show significant variation
across taxa. Deeper analysis of the reported data to understand the cause of this variation was
not possible; we have therefore taken the data at face value.
For the kiwi taxa and management regimes for which we have no community reports, we
applied average costs of items from reported K4K data to produce estimates of additional
annual costs of the management regimes and conservation scenarios. This was done for the
(very small) community management of Fiordland and Rakiura tokoeka, and for the use of
toxins for western brown. Thus, for these taxa and management regimes, the cost estimates of
additional management are based on national cost averages, not taxon-specific data.
The K4K data distinguish between funded and volunteered hours spent on various activities
and the equipment in use. In addition, we assume communities do not account for capital
wear and tear by preparing for capital replacement. The full economic cost of kiwi
conservation is therefore higher than the current level of funding, and we report on this
‘volunteer contribution' for the current situation.
For the ‘sustainable trapping with poison’ regime, we allocate appropriate reported cost items
from the K4K data to this regime and derive a per-hectare cost. In this approach we assume
time and equipment used in the scenarios increase linearly with kiwi distribution (hectares)
based on the number of birds in the first year (see 4.3.3) and that the ratio of funded and
volunteered effort remains stable with additional management.
Under the status quo, we assume communities apply continuous trapping with pulsed poison
operations. This is probably unlikely in many instances, but the K4K data do not allow us to
identify the poisoning practices that communities use.
The community-reported data cover a wide range of equipment and activities. Not all these
relate directly to the management regime ‘sustained trapping with poisoning’. Advocacy, for
instance, is important both in attracting volunteers and funding, and in making the wider
population more aware of how they might unwittingly affect kiwi populations. However,
there is no basis for saying that advocacy will increase with more trapping. Hence, we do not
include such indirect cost items in the estimate of the cost of achieving population growth or
stability.
Predator exclusion fences help to protect kiwi as well as other species inside the fenced area,
so ideally we would have allocated a share of the costs to kiwi, but there is no meaningful
basis to do so. Given that the maintenance and depreciation of these fences is likely to
continue regardless of kiwi, we decided to exclude fence costs from the analysis.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 21
The kohanga regime is assumed to continue at the cost level of the status quo. Additional
costs arise from transferring birds to the kohanga sites, other than for Fiordland and Rakiura
tokoeka, which we assumed to be managed by DOC (see below), and have not been included
in the analysis. Here, for the sake of simplicity, we assume that each transferred bird has a
one-off cost of $1,000, and that the full number of additional birds is transferred in the first
year. In practice this is unlikely to be possible.
The increased number of kiwi under a given management regime provides the additional area
and cost for that regime under each conservation scenario via derived bird densities. These
bird densities are based on our expert opinion that 95% of kiwi populations inhabit 30% (for
‘the brown kiwi’) and 60% (great spotted kiwi, Fiordland and Rakiura tokoeka) of the
potential habitat. We assume that the management regimes target kiwi populations with
higher bird densities, which limits the extra area that is required under the additional
management to achieve stability and growth.
We additionally assume that the area under management does not increase after the first year,
i.e. additional birds do not disperse beyond the boundaries of new and old conservation sites.
This implies that the bird densities in such areas can increase without limit under the new
management to achieve stability and growth. This may not reflect ecological reality and
expanding managed areas may prove to be necessary. However, threshold bird densities to
trigger such expansion could not be modelled in this project. The assumption implies that the
cost estimates may well be underestimates of the actual additional conservation funds
required.
5.1.1 How this report handles DOC costs
DOC currently receives NZ$1.7 million annually to run the five Kiwi Sanctuaries. Of these
funds, around NZ$850,000 is allocated to the Ōkārito and Haast Kiwi Sanctuaries, where
ONE is a significant share of the expenditures. The Kiwi Sanctuaries for Northland
(Whangārei), Coromandel (Moehau) and western brown kiwi (Tongariro) share the
remaining portion of the budget. Funds are spent on staff, research, toxins, traps, and other
equipment, such as quad bikes and radio transmitters. No specific information was found
about expenditure for the management of little spotted kiwi.
With the exception of aerial 1080, it was beyond the scope of this report to obtain reliable
DOC costs per regime, or to obtain reliable DOC costs per taxon. Our assumption is that
DOC expenditures, e.g. for kiwi sanctuaries, research, and Community Conservation
Partnership Funding to kiwi projects, remain at their current levels. Therefore: 1) we derived
the annual cost of current management per taxon for community groups only; 2) we derived
costs of additional management using trapping and poisoning cost data not from DOC but
from community groups, unless otherwise stated; and 3) in the analysis of annual current
costs, we exclude taxa managed primarily by DOC (little spotted, rowi, Haast, Fiordland, and
Rakiura).
We note that the involvement of DOC staff in community conservation efforts is likely to
raise the (labour) cost of kiwi conservation significantly (see Appendix 1, ‘Time’), compared
with funded and volunteered actions by community conservation groups.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 22 Landcare Research
5.2 Annual cost of current management
For the current management scenario, we used the K4K reported data on, e.g. the time spent
on activities and the number of traps used to estimate the cost of the current kiwi
conservation effort. Thus, we have a baseline cost against which the other scenarios can be
evaluated. Table 6 provides a summary of community costs for the five kiwi taxa with
substantial community involvement, but excludes DOC expenditures as explained above.
The management cost of kohanga kiwi differs across taxa, with particularly high costs for
eastern and western brown. In both cases, a large amount of time was reported for checking
bait stations. For all kiwi taxa, the combined total annual cost of kohanga is just over
$616,000.
Kohanga sites for eastern and western brown have long stretches of pest-fencing that benefits
kiwi as well as other species. A share of annual fence maintenance and depreciation costs
could be allocated to kiwi conservation, but we have no way to determine the size of that
share. We can note, however, that our cost estimate for kohanga sites is low because our
estimates exclude pest-fence costs.
Table 6 Estimates of annual costs reported by communities for management of the five kiwi taxa with
substantial community involvement, derived by applying data collected by K4K to the status quo. Costs are split
between kohanga kiwi and other community-led conservation activities. For community activities, a further
distinction is made between costs for trapping and poisoning, and indirect costs such as advocacy and general
capital. The ‘T&P/I ratio’ indicates how many dollars are spent on trapping and poisoning per dollar spent on
indirect costs (higher ratio means more money is spent on predator control). ‘Total’ indicates the sum of funded
(e.g. contracted) and volunteered conservation actions, and unfunded capital depreciation. The ‘donated
resources’ expresses the share of volunteered and uncosted contributions to the total conservation effort
Kiwi taxa Kohanga total
($)
Community Trapping & poison total
($)
Indirect total
($)
T&P / I ratio All costs total
($)
Donated resources
(%)
Great spotted 0 175,448 456,952 0.38 632,400 24.9
Northland 54,408 1,696,309 1,507,447 1.13 3,203,756 37.9
Eastern 154,612 383,806 452,771 0.85 836,577 55.8
Western 386,840 437,547 416,171 1.05 853,718 44.7
Coromandel 20,552 352,252 399,153 0.88 751,405 59.3
All taxa 616,411 3,045,363 3,232,493 0.86 6,277,856 44.5
Since indirect costs may not be directly related to controlling predators per se, it is possible
that these costs are stable regardless of the level of trapping and poisoning. These costs could
be regarded as ‘overhead’ or fixed costs of enabling predator control. The ‘TP/I’ ratio shows
that, for all taxa combined, for every dollar spent on administration, advocacy, etc, $0.86 is
spent on predator control.
This suggests community groups spend more time procuring funding, raising awareness and
carrying out administrative tasks, than they do on predator control. Groups managing
Northland brown have low indirect costs, whereas groups managing great spotted kiwi report
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 23
higher indirect costs. Further data and research will be required to understand the cause of
these differences and to develop potential guidelines.
The total (trapping and indirect) annual cost of community-actioned kiwi conservation is $6.3
million. By far the highest financial effort is put into the conservation of Northland brown
kiwi; eastern, western, and Coromandel brown get less, and great spotted receives the
smallest community conservation effort of these taxa. For Fiordland and Rakiura tokoeka, we
have no community reports.
Of this $6.3 million, community groups contribute around 44% in voluntary contributions on
average. This proportion is 59% for groups managing Coromandel browns and 25% for
groups working with great spotted kiwi.
The bulk of the voluntary contribution is volunteer time. Although trap depreciation (‘saving
for replacement’) can run into thousands of dollars for some groups, it is a small cost
compared with the time volunteers spend on checking and setting traps. Consequently,
keeping up advocacy is necessary to recruit new volunteers. Additionally, community
funding is generally short term and re-application for funding may be needed at intervals (M.
Impey, K4K, pers. comm.). Community groups continuously need to develop and secure
funding to continue operations.
These deductions may partially explain our finding that community groups spend less on
predator control than on, say, administration. There may be a self-sustaining element of
overhead costs in kiwi conservation that could be reduced by providing community groups
with more long-term financial security. This would allow groups either to focus more on
predator control or to reduce costs. Developing options for new funding models could be one
area for further research.
5.3 Additional cost of population stability and growth targets
In this section, we estimate the additional cost of achieving 0% (i.e. stability) and 2% growth
p.a. under various model parameter choices and conservation scenarios compared to the
status quo.
Over 15 years, these costs represent a significant investment commitment, which can inform
decision-making on options for kiwi conservation or research investments. We provide the
(temporally weighted) present value of the annual costs of the 15-year period of the
population model, discounted at 10% (the temporal weighting factor). We also provide the
present value at a 5% and 15% discount rate to show how the discount rate affects the present
value.
The costs for the management regime ‘ONE’ were taken from Gillies et al. (2013). The costs
for kohanga are based on DOC experience. The costs for the ‘sustained trapping and
poisoning’ regime come from the K4K reported data (total annual trapping and toxin costs).
The costs for ‘aerial poisoning’ are based on expert assessment of the numbers reported in
PCE (2013).
As discussed above, for Fiordland and Rakiura tokoeka and western brown, some costs of the
management regimes are national averages rather than specific to these taxa. Coromandel
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 24 Landcare Research
brown requires no extra effort under any of the parameter choices (Table 2) and is therefore
not shown here.
Note that the results are estimates of costs that are additional to the status quo (estimated
$6.3 million plus current DOC expenditures on kiwi conservation). This illustrates the extra
financial effort that is needed to achieve the conservation targets, and as noted above, most
costings (but not aerial 1080) use community group data. If the current funding and volunteer
contributions do not continue at current levels, the need for additional funding increases
accordingly.
5.3.1 Northland
Northland brown only requires additional conservation effort in the parameter choices of a
2% p.a. growth target and low growth rates. The estimate of additional annual cost compared
with the status quo is shown in Figure 3. Sustained trapping with pulses of poison baiting are
the only management regime, which has an additional annual cost of around $410,000.
Figure 3. Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for Northland
brown kiwi. In this and following graphs, $0 cost (no graph bars) means that the taxon population
already achieves 0% or 2% growth p.a. (Table 2).
The present value of the additional annual costs of this scenario in the 15-year period is just
over $3.5 million ($2.9m – $4.6m; 15% and 5% discount rate, respectively).
5.3.2 Western
Western brown requires additional conservation effort under most of the parameter choices
for the 2% p.a. growth target. For this taxon, and for eastern, we show two alternative
conservation scenarios, one emphasizing aerial 1080 (Fig. 4) and a second emphasizing
trapping (Fig. 5), simply to illustrate the financial impact of alternative ways to recover kiwi
populations.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 25
Figure 4. Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for western
brown kiwi, mainly using aerial 1080 poisoning.
One conservation scenario mainly using aerial poisoning operations leads to high additional
annual costs, which may require as much as $1.3 million extra funding under the low-growth
parameter choices (Fig. 4). Under the best-guess parameter choices, the additional annual
costs are $495,000. Growth rates with this management regime are low and hence large areas
need to be managed to increase the population. In addition, these costs are incurred every 3
years.
With the low initial population parameter choice, 2% growth p.a. can be achieved by
increasing aerial poisoning but reducing sustained trapping, which results in a negligible
(nett) additional annual cost. This is indicated by comparing the green bar below the x-axis
line and the purple bar above it in the ‘2% Low initial population’ parameter choice.
Management under this parameter choice is much cheaper than under the ‘2% High initial
population’ parameter choice because with a low population a higher proportion of kiwi are
under regimes such as ONE and kohanga, and so the share of the population that needs
additional management is smaller than with a high population.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 26 Landcare Research
Figure 5. Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for western
brown kiwi, mainly using community trapping.
Figure 5 shows the estimated annual costs for an alternative allocation of kiwi to management
regimes which emphasises the use of kohanga kiwi and sustained trapping. With every choice
of parameters and conservation scenario, the additional annual costs are much lower than
those 1080 costs shown in Figure 4, because growth rates are higher under trapping (1.06, i.e.
6% p.a.) than aerial 1080 every 3 years (1.02, Table 2), and because communities mostly
volunteer their labour. Particularly for the low initial population parameter choice, placing
more birds in kohanga means the conservation target can be achieved with fewer birds under
trapping or aerial poisoning management. A nett annual cost saving of just under $300,000 is
the result. The other scenarios show additional annual costs of between $90,000 and
$554,000.
The present value of the additional costs using the best-guess parameter choices to achieve
the 2% p.a. growth target in the total 15-year period under the aerial 1080 conservation
scenario (Fig. 4) is $4.5 million ($3.8m – $5.7m; 15% and 5% discount rate, respectively).
The present value of the additional costs under the low-growth parameter choice is $11.8
million ($9.9m – $14.7m).
The present value of the additional costs using the best-guess parameter choices to achieve
the 2% p.a. growth target in the total 15-year period under the mainly-trapping scenario
(Fig. 5) is just over $842,000 ($713,000 – $1 million). The present value of the additional
costs under the low-growth parameter choice is $4.7 million ($3.6m – $5.6m).
5.3.3 Eastern
Eastern brown requires additional conservation effort under all scenarios to reach the 2% p.a.
growth target, and with the low growth parameter choice for the 0% p.a. growth target. The
estimate of additional annual cost compared with the status quo is shown in Fig. 6 for one
conservation scenario of allocating birds to management regimes, which emphasises aerial
poisoning operations.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 27
Figure 6. Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for eastern
brown kiwi, primarily using aerial 1080.
Under this allocation, the 0% growth p.a. target under the low-growth parameter choice has
an additional annual cost of $1 million. The best-guess parameter choice for the 2% growth
p.a. target has an additional annual cost of 1.9 million, whereas the low-growth parameter
choice costs $3.4 million additional to current funding.
Figure 7 shows the additional annual costs under an alternative allocation of birds to
management regimes. In this conservation scenario, the kohanga kiwi and sustained trapping
and toxin regimes are cheaper than aerial poisoning operations.
Figure 7. Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for eastern
brown kiwi, primarily using trapping.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 28 Landcare Research
For the 0% growth p.a. target, the low-growth parameter choice carries an additional annual
cost of just under $427 000. Using best-guess parameter choices for the 2% growth p.a. target
has an additional annual cost of just over $322 000, and the low-growth parameter choice is
the most costly at $832 000 over the current expenditures.
Using mainly aerial 1080 (Fig. 6), the present value of the additional costs of the low-
growth parameter choice for the 0% p.a. growth target for the whole 15 years is $9.3 million
($7.8m – $11.6m; 15% and 5% discount rate, respectively). For the 2% growth p.a. target,
the present value of the additional costs under best-guess parameter choices is $17.6 million
($14.7m – $21.9m), and $31.6 million ($26.4m – $39.4m) under the low-growth parameter
choice.
The present value of the additional costs with the low-growth parameter choice for the 0%
growth target p.a. using mainly trapping (Fig. 7) for the whole 15 years is $2.6 million
($2.1m – $3.4m; 15% and 5% discount rate, respectively). For the 2% p.a. growth target, the
present value of the additional costs under the best-guess parameter choice is $2.8 million
($2.3m – $3.6m), and $7.2 million ($5.9m – $9.3m) under low-growth parameters.
5.3.4 Great spotted
Great spotted kiwi requires additional conservation effort under all parameter choices,
regardless of the growth target. The 2% p.a. growth target cannot be achieved under the low-
growth parameter choice because ONE is unlikely to be practical; kohanga space on islands is
zero or limited; trapping opportunities are limited by terrain and access, and it may be hard to
get 2% growth from aerial 1080 alone. In all viable scenarios, the emphasis is on aerial
poisoning operations because of the remote and rugged landscape that great spotted inhabit.
The estimate of additional annual cost compared to the status quo is shown in Figure 8.
Figure 8. Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for great
spotted. The 2% p.a. growth target cannot be achieved under the low growth parameter choice, and is marked
with a red cross.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 29
For the 0% p.a. growth target, the best-guess parameter choice has an additional annual cost
of $1.5 million. The high initial population parameter choice carries the highest additional
annual cost of $2.1 million. For the 2% p.a. growth target, the best-guess parameter choice
has an additional annual cost of $4.2 million, and the high initial population parameter choice
has the highest additional annual cost of $5.5 million.
The present value of the additional costs of the best-guess parameter choice for the 0% p.a.
growth target for the whole 15 years is $17.5 million ($15m – $21.4m; 15% and 5% discount
rate, respectively), and for the high initial population parameter choice it is $23.8 million
($20.5m – $29.2m). For the 2% p.a. growth target, the present value of the 15-year additional
costs of the best-guess parameter choice is $37.6 million ($31.4m – $47m); for the high
initial population parameter choice it is $49.8 million ($41.6m – $62.1m).
5.3.5 Fiordland
Fiordland tokoeka require additional conservation effort under all parameter choices,
regardless of the growth target. The 2% p.a. growth target cannot be achieved with low-
growth parameters. In all viable scenarios, the emphasis is again on aerial poisoning
operations because of their remote and rugged habitat, and the sparseness of local
communities. Kohanga sites are remote and it will be difficult to locate and transfer surplus
kiwi to mainland sites. The estimate of additional annual cost compared to the status quo is
shown in Figure 9.
For the 0% p.a. growth target, the best-guess parameter choice has an additional annual cost
of just over $847,000. The low-growth parameter choice carries the highest additional annual
cost of $1.4 million. For the 2% p.a. growth target, the best-guess parameter choice has an
additional annual cost of $2.9 million, and the high-initial population parameter choice has
the highest additional annual cost of $3.8 million.
The present value of the additional costs of the best-guess parameter choice for the 0% p.a.
growth target for the whole 15 years is $7.8 million ($6.5m – $9.7m; 15% and 5% discount
rate, respectively), and for the low-growth parameter choice it is $13 million ($10.9m –
$16.1m). For the 2% p.a. growth target, the present value of the additional 15-year costs of
the best-guess parameter choice is $26.7 million ($22.3m – $33.2m); for the high initial
population parameter choice it is $34.8 million ($29.1m – $43.3m).
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 30 Landcare Research
Figure 9 Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for Fiordland
tokoeka. The 2% p.a. growth target cannot be achieved under the low growth parameter choice, and is marked
with a red cross.
5.3.6 Rakiura
Rakiura tokoeka require additional conservation effort under all parameter choices, regardless
of the growth target. In all but two conservation scenarios, the emphasis is on poisoning using
bait stations. For the 2% p.a. growth target, two scenarios also make significant use of the
sustained trapping and poison regime. There are kohanga options such as Pearl, Codfish and
Big South Cape Islands, but the ecological impact of introducing Rakiura tokoeka would
have to be assessed carefully. The estimate of additional annual cost compared to the status
quo is shown in Figure 10.
Figure 10 Estimate of annual costs additional to the status quo to achieve 0% and 2% growth p.a. for Rakiura
tokoeka.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 31
For the 0% p.a. growth target, with best-guess parameters there is an additional annual cost of
just under $250,000. With low-growth parameters, there is the highest additional annual cost
of just under $406,500. For the 2% p.a. growth target, the best-guess parameter choice has an
additional annual cost of just over $607,000, and the low-growth parameter choice has the
highest additional annual cost of just over $773,000.
The present value of the additional costs with best-guess parameter choices for the 0% p.a.
growth target for 15 years total is $2.3 million ($1.9m – $2.8m; 15% and 5% discount rate,
respectively), and with low-growth parameters it is $3.7 million ($3.1m – $4.6m). For the 2%
p.a. growth target, the present value of the additional 15-year costs with best-guess
parameters is $5.6 million ($4.7m – $6.9m); with low-growth parameters it is $7 million
($5.8m – $8.8m).
5.3.7 All kiwi taxa that require additional resources to achieve 0% or 2% p.a. growth
For all kiwi taxa that require additional resources to achieve 0% p.a. population growth, the
additional annual cost with best-guess parameters is $2.6 million. Under these parameters,
only great spotted kiwi and Fiordland and Rakiura tokoeka require additional conservation
effort. The low-growth rate parameter choice has the highest additional annual cost ($3.9m),
and the low initial population and the high growth parameter choices have the lowest
additional cost ($1.7m).
The present value (10% discount rate) of the additional, cumulative, 15-year cost of halting
decline for these three parameter choices (low growth rate, low initial population and high
growth rate) are, respectively, $27.5 million, $38.5 million, and $18 million.
To achieve the 2% p.a. growth target with best-guess parameters carries an additional annual
cost of $8.1 million. The low-growth parameter choice was not costed because the
conservation target cannot be achieved for Fiordland tokoeka and great spotted kiwi. The
parameter choice with the highest cost is ‘high initial population’ ($11.3m).
The present value of the additional cost with these three parameter choices are, respectively,
$73.5 million, $22.5m, and $102m.
6 Discussion
Mammalian predators are the key cause of kiwi declines and range limitation, and all
unmanaged populations on the New Zealand mainland are declining, albeit at different and
sometimes little known rates (McLennan et al. 1996; Holzapfel et al. 2008; Robertson et al.
2011). Protecting habitat without reducing predation will not recover kiwi. Discussions
between major kiwi recovery partners are required to decide where, when, how and by whom
populations should be managed.
Increasing the scale of cost-effective pest control is a clear requirement for kiwi recovery, as
it is for restoration of most other New Zealand biodiversity. Small or mid-sized accessible
populations that have most birds managed (Haast, rowi, little spotted, Coromandel,
Northland) are increasing most rapidly, whereas large, remote populations with few birds
managed (Rakiura, great spotted, Fiordland) are declining most rapidly. This shows the
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 32 Landcare Research
benefit of past kiwi recovery focus on the most threatened taxa, due to a team effort of DOC,
K4K, conservation agencies such as Forest and Bird, corporate sponsors such as BNZ, and
many communities. If our input data are correct, the eastern brown kiwi is finely poised
between increase and decline (Fig. 11).
Figure 11. Relationship between estimated current growth rate p.a. (mean over 15 years) with ‘best-guess’
parameters and proportion of birds in each population managed, for all 10 kiwi taxa. The horizontal dashed line
shows rate = 1.0 at which populations do not grow. Populations above this line are estimated to be increasing;
those below it are declining.
While this report has by necessity presented more detail about community than DOC costs,
both (and other) parties will be needed if all kiwi are to be managed to achieve 2% growth
p.a. New kiwi conservation work can be done either by community groups or by DOC,
although they probably have different intrinsic strengths. Communities can trap more
cheaply if they use volunteer labour, while DOC is an experienced organiser of aerial 1080
drops. Research and taxon recovery planning are also key DOC roles. The inevitable funding
shortfall between current (even including the Budget 2015 boost) and required levels to
achieve 2% p.a. growth has to be sought from somewhere – Government, communities,
individuals or corporates of various kinds. Many options are possible.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 33
6.1 Adequacy of input kiwi data
As with most birds in New Zealand and elsewhere, actual densities or total sizes of kiwi
populations are not known precisely. This apparent shortfall persists because there are no
cost-effective techniques for counting kiwi. Determining actual population sizes is probably
technically feasible but may consume most of the kiwi management budget, and so is poor
value for money. Trained dogs can find kiwi and there are some data about their success rate,
but it is an inefficient method unless densities are high (Robertson & Fraser 2009). Most
populations are monitored with call counts (Pierce & Westbrooke 2003), which index but do
not enumerate actual population size. There is increasing use of automated recorders that can
be placed in the field and analysed by computers for kiwi calls (Digby et al. 2013) but they
generally do not detect as many calls as human listeners and do not allow estimation of
numbers of different birds calling in an area. We suggest that not knowing actual population
sizes is no impediment to kiwi recovery, although obtaining reliable knowledge about how
changes in call rate indices relate to changes in actual kiwi numbers at different densities is
important to enable accurate reporting on conservation outcomes.
The most critical uncertainty in our models is growth rates associated with each of the key
regimes, but particularly with trapping and aerial (or ground) poisoning. Most of the
population growth rates we present have not been directly measured for each taxon. Further
clarification of these is clearly required. Surely the best opportunity for this is to monitor kiwi
numbers during actual management programmes using the major regimes, in an adaptive
management framework. Uncertainty will remain about outcomes until this and other
research are undertaken.
6.2 Kiwi modelling assumptions
We assume that population growth rates associated with each management regime do not
improve with time, but in practice they should, with new technologies, toxins, and disciplines
(e.g. revised or enforced ‘best practice’, pest management Standard Operating Procedures).
Other assumptions listed in 4.2.3 have varying reasonableness. In practice, some kiwi
dispersal outside managed areas is highly likely if the areas are small; preliminary estimates
of natal dispersal distances for eastern brown were at least 5 km, and it is unknown if
dispersal is density dependent (Basse & McLennan 2003), but distances were smaller in
Northland (Robertson et al. 2011).
6.3 Selecting growth scenarios and preferred management techniques
There will rarely be one ‘right answer’ about where or how to manage kiwi, especially if their
current distribution (the geographic range they occupy) is still large. The suggestions we
make in this report are just that; many alternatives are possible. We hope that the spreadsheet
tools developed during this project can be used in a dynamic and iterative way to support
decision-making.
Selecting where to manage kiwi can greatly affect costs. Applying trapping or aerial
poisoning to sites with high kiwi density will increase kiwi benefits for a given pest control
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 34 Landcare Research
cost. However, we suggest that people should choose to manage areas with room for
population growth, to avoid carrying capacity (or K) effects. K will vary from site to site,
and may also be affected by the removal of competitors such as ship rats and hedgehogs
(Erinaceus europaeus).
Different pest control tools also have quite different outcomes for other biodiversity. For
example, adding 200 birds to kohanga at Cape Sanctuary now could relieve 1000 others from
requiring aerial 1080 to achieve the same kiwi outcome, but aerial 1080 would undoubtedly
have broader ecosystem benefits than increasing kohanga birds in this way. Note that having
100 birds in the Cape Sanctuary now is predicted to result in having 400+ kiwi there in 15
years. The same may be said of stoat trapping to benefit kiwi. This regime by itself may
protect other stoat-vulnerable taxa, such as whio (Hymenolaimus malacorhynchos)
(Whitehead et al. 2008) and takahe (Porphyrio hochstetteri) (Hegg et al. 2012), but few
others, especially if ship rats (Rattus rattus) increase after stoats (their main predator) are
reduced (Blackwell et al. 2003). DOC and community groups may therefore have different
management preferences, because they have different legal obligations, social contexts, and
probably skills, knowledge, and resources.
The comparison of management options for western (5.3.2) and eastern (5.3.3) browns
showed that with volunteer labour, trapping was cheaper than aerial 1080, but this trapping
targeted mustelids (mainly stoats) only, while aerial 1080 is also an effective tool against the
much more abundant ship rats and possums.
6.4 Community conservation and cost modelling
Given the many uncertainties in the cost data that we have used in this report, our resultant
estimates should be seen as preliminary, and should be updated as better information comes
to hand.
Regarding the cost estimates of community conservation, this study relies on the community-
reported data gathered by K4K. There are significant differences in the total cost and cost
structures for each taxon. It is possible that the survey questions for this novel reporting
exercise were not sufficiently clearly defined, leaving room for interpretation and thus
reporting errors. Examples are that community groups sometimes included largely irrelevant
(to kiwi) rat control costs with kiwi kohanga management, and that they were asked to
estimate the areas (in hectares) that were protected by stoat trapping grids, which is a difficult
calculation. Also, there was no application of a ‘best practice’ sieve on community data, so
that the very diverse trap networks and regimes were treated as having the same pest and kiwi
outcomes, and mean costs were used to estimate costs of future management.
K4K should develop its questionnaire to elicit more kiwi-specific community actions and
costs, and repeat the survey on a regular basis. In due course, the improved and repeated data
would provide K4K with better information to analyse how the funds it distributes are spent,
helping it to allocate its resources more effectively.
A tentative result from analysing the data, for instance, is that communities, like DOC, spend
more time and funds on administration, advocacy, and other expenditures than they do on
predator control. While these activities are undoubtedly necessary under the current realities
for communities’ funding (see next section), lowering these costs is likely to bring the total
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 35
cost of kiwi conservation down by some margin: on average, for every dollar spent on
supporting activities, 86 cents are spent on predator control, the main support for kiwi
populations. This calculation includes volunteered time, costed at ca $21 per hour (see Time
in App. 2).
The benefits of the research directions described below are therefore relevant not just for
kiwi, but also for the government purse. With better monitoring and awareness of areas where
kiwi can flourish, conservation efforts can be targeted to achieve a higher cost-effectiveness.
Improved techniques for predator control will lower costs and bring down the funding
required to maintain populations and conserve kiwi. Since kiwi are not the only species that
would benefit from such research efforts, the synergies with the conservation of other species
imply that overall conservation costs might be brought down significantly.
The cost modelling assumed that the DOC contribution to kiwi conservation is maintained at
current (2014/15) levels and that the new money granted in Budget 2015 for 2015/16 onward
is indeed additional funding and not used to replace existing budget streams such as the Kiwi
Sanctuary programme and Community Conservation Partnership Funding.
6.5 Additional funding required to halt declines and achieve 2% growth p.a.
Our preliminary analysis suggests that significant additional funding is required to achieve
either of the stretch conservation targets. For the scenarios we used, and assuming best-guess
input data, funding of around $2.6 million annually on top of current funding is needed for
the next 15 years to halt kiwi declines. To achieve 2% growth p.a. of all 10 taxa, additional
funding of around $8.1 million annually is needed for the same period.
The recently-announced new funding package for kiwi conservation in Budget 2015 has an
injection of $11.2 million over the next 4 years but in the fourth year and thereafter $6.8
million per annum will be available for kiwi conservation. This should allow stable
populations to be achieved, with a remaining shortfall of $1.3 million per annum to achieve
2% growth p.a. across the board.
These cost figures are minimum estimates for a number of reasons. First, trapping costs are
based on rates for contractors and community volunteers. Stronger involvement of DOC staff
will raise the labour costs by some margin. Second, according to our data, more extensive use
of aerial poisoning operations will raise costs significantly. Third, for reasons outlined in 5.1,
the costs of pest-fences were not included but these could become significant if large fence-
lengths were allocated entirely to kiwi recovery.
The ratio of indirect costs and costs for predator control was mentioned above. Indirect
activities allow community conservation groups to recruit volunteers and attract funding. In
the K4K questionnaire, communities reported on time and expenditures that are currently
funded, which on average were 44% of the total cost. Not all these funds are secure for long
periods of time, forcing communities to search continuously for new funding when other
sources run out.
This suggests that kiwi conservation costs might be reduced by structuring funding in such a
way that communities are under less pressure to pursue funding or contribute out of their own
pocket. Such a funding structure could take many forms. In the current situation, it may be
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 36 Landcare Research
beneficial if seeking funding is undertaken strongly by one organisation, such as K4K, that
might more efficiently engage with (e.g. corporate) funders than individuals.
6.6 Priority research and monitoring
Research to clarify the taxonomic status of the actual or perceived taxonomic units that we
have referred to as ‘taxa’ of kiwi in this report is needed to guide where management effort
should be prioritised.
As discussed above, future management decision-making would be greatly helped by more
structured investigation into growth rates of different kiwi populations under the major pest
management regimes identified here. This requires effective population monitoring tools.
Research should continue on the reliability of call-count indices, including examining the
efficacy of using automatic recorders (and analysing recordings to find kiwi calls), and the
ratios between call counts and actual kiwi numbers at varying densities. Verifying that call
counts can accurately determine underlying population trends would greatly help instil
confidence that different management regimes could be evaluated in that way. Other means
of monitoring kiwi, including faecal DNA and acoustic recorders, should also be explored.
Improved control techniques are required for key mammal pests, particularly stoats, but also
ferrets, and feral cats. This control should include better lures and baits, better traps
(including multiple kill), optimal sowing rates for 1080, and new toxins. It is particularly
valuable at the moment for kiwi managers to support the registration for aerial distribution of
the toxin para-aminopropiophenone (PAPP), and the development of suitable kiwi-proof baits
for that purpose. Further research is also needed on the effectiveness of dog aversion training
(Dale et al. 2013).
More complete and accurate costing of kiwi recovery will depend on improving the quality of
cost data from communities, and on obtaining full kiwi management and monitoring costs
from DOC. These will frequently be complicated by the fact that management of one species
such as a kiwi taxon (e.g. by pest-fencing) sometimes targets many others as well, so that
determining what proportion of costs should be allocated to kiwi is at best very difficult.
7 Acknowledgements
We thank Rogan Colbourne (Department of Conservation) for conversations about kiwi
ecology and management. We also thank reviewers whose comments greatly improved
versions of this manuscript: Andrea Byrom, Mario Fernandez, Jennifer Germano, Suzie
Greenhalgh, Michelle Impey, John McLennan, Henrik Moller, Carol West and Roger Pech.
Thanks also to Cynthia Cripps and Anne Austin for help with formatting and editing
respectively. Finally we thank the hard-working community group members who supplied
cost and population data to K4K for this work, and Michelle Impey of K4K for facilitating
that.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 37
8 References
Baker AJ, Daugherty CH, Colbourne RM, McLennan JA 1995. Flightless brown kiwis of
New Zealand possess extremely subdivided population structure and cryptic species
like small mammals. Proceedings of the National Academy of Sciences of the United
States of America 92: 8254–8258.
Basse B, McLennan JA 2003. Protected areas for kiwi in mainland forests of New Zealand:
how large should they be? New Zealand Journal of Ecology 27: 95–105.
Blackwell GL, Potter MA, McLennan JA, Minot EO 2003. The role of predators in ship rat
and house mouse population eruptions: drivers or passengers? Oikos 100: 601–613.
Brown MA, Stephens RTT, Peart R, Fedder B 2015. Vanishing nature: facing New Zealand's
biodiversity crisis. Environmental Defence Society, New Zealand.
Brown K, Urlich S 2005. Aerial 1080 operations to maximise biodiversity protection. DOC
Research and Development Series 216. Wellington, New Zealand, Department of
Conservation.
Burbidge ML, Colbourne RM, Robertson HA, Baker AJ 2003. Molecular and other
biological evidence supports recognition of at least three species of brown kiwi.
Conservation Genetics 4: 167–177.
Butler D, McLennan JA 1991. Kiwi Recovery Plan. Threatened Species Recovery Plan 2.
Wellington, New Zealand, Department of Conservation.
Colbourne R, Bassett S, Billing A, McCormack H, McLennan J, Nelson A, Robertson H
2005. The development of Operation Nest Egg as a tool in the conservation
management of kiwi. Science for Conservation 259. Wellington, New Zealand,
Department of Conservation.
Colbourne RM, Robertson HA 1997. Successful translocations of Little spotted kiwi (Apteryx
owenii) between offshore islands of New Zealand. Notornis 44: 253–258.
Dale AR, Statham S, Podlesnik CA, Elliffe D 2013. The acquisition and maintenance of dogs'
aversion responses to kiwi (Apteryx spp.) training stimuli across time and locations.
Applied Animal Behaviour Science 146: 107–111.
Digby A, Towsey M, Bell BD, Teal PD 2013. A practical comparison of manual and
autonomous methods for acoustic monitoring. Methods in Ecology and Evolution 4:
675–683.
Gillies R, McClellan R, Rate S 2013. Operation Nest Egg situation analysis. Unpublished
Wildlands Consultants Contract Report 2999.
Hegg D, Greaves G, Maxwell JM, MacKenzie DI, Jamieson IG 2012. Demography of takahe
(Porphyrio hochstetteri) in Fiordland: environmental factors and management affect
survival and breeding success. New Zealand Journal of Ecology 36: 75–89.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 38 Landcare Research
Herbert J, Daugherty CH 2002. Genetic variation, systematics and management of kiwi
(Apteryx spp.). In: Overmars F ed Some early 1990s studies in kiwi (Apteryx spp.)
genetics and management. Science and Research Internal report 191. Wellington, New
Zealand, Department of Conservation. Pp.10–33.
Holzapfel S, Robertson HA, McLennan JA, Sporle W, Hackwell K, Impey M 2008. Kiwi
(Apteryx spp.) recovery plan 2008–2018. Threatened Species Recovery Plan 60.
Wellington, New Zealand, Department of Conservation.
Jones BM 2006. Assessing the effectiveness of a Department of Conservation procedure for
training domestic dogs to avoid kiwi. Science for Conservation 267. Wellington, New
Zealand, Department of Conservation.
McLennan JA, Potter MA, Robertson HA, Wake GC, Colbourne R, Dew L, Joyce L,
McCann AJ, Miles J, Miller PJ, Reid J 1996. Role of predation in the decline of kiwi,
Apteryx spp, in New Zealand. New Zealand Journal of Ecology 20: 27–35.
Norbury G, Hutcheon A, Reardon J, Daigneault A. 2014. Pest fencing or pest trapping: A
bio-economic analysis of cost-effectiveness. Austral Ecology 39: 795–797.
Ornithological Society of New Zealand 2010. Checklist of the birds of New Zealand, Norfolk
and Macquarie islands, and the Ross Dependency, Antarctica.Wellington, New
Zealand, Te Papa Press.
PCE 2011. Evaluating the use of 1080: Predators, poisons and silent forests. Wellington, New
Zealand, Parliamentary Commissioner for the Environment.
PCE 2013. Evaluating the use of 1080: Predators, poisons and silent forests. Update report.
Wellington, New Zealand, Parliamentary Commissioner for the Environment.
Pierce, RJ, Westbrooke IM 2003. Call count responses of North Island brown kiwi to
different levels of predator control in Northland, New Zealand. Biological Conservation
109: 175–180.
Ramstad KM, Colbourne RM, Robertson HA, Allendorf FW, Daugherty CH 2013. Genetic
consequences of a century of protection: serial founder events and survival of the little
spotted kiwi (Apteryx owenii). Proceedings of the Royal Society B-Biological Sciences
280: 20130576. http://doi.org/10.1098/rspb.2013.0576.
Robertson HA, Colbourne RM, Graham PJ, Miller PJ, Pierce RJ 2011. Experimental
management of brown kiwi Apteryx mantelli in central Northland, New Zealand. Bird
Conservation International 21: 207–220.
Robertson HA, Colbourne RM, Nelson A, Westbrooke IM 2006. At what age should brown
kiwi (Apteryx mantelli) eggs be collected for artificial incubation? Notornis 53: 229–
232.
Robertson HA, Dowding JE, Elliott GP, Hitchmough RA, Miskelly CM, O'Donnell CFJ,
Powlesland RG, Sagar PM, Scofield RP, Taylor GA 2013. Conservation status of New
Zealand birds, 2012. New Zealand Threat Classification Series 4. Wellington, New
Zealand, Department of Conservation.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 39
Robertson HA, Fraser JR 2009. Use of trained dogs to determine the age structure and
conservation status of kiwi Apteryx spp. populations. Biological Conservation
International 19: 121–129.
Robertson HA, de Monchy PJM 2012. Varied success from the landscape-scale management
of kiwi Apteryx spp. in five sanctuaries in New Zealand. Bird Conservation
International 22: 429–444.
Whitehead AL, Edge K-A, Smart AF, Hill GS, Willans MJ 2008. Large scale predator
control improves the productivity of a rare New Zealand riverine duck. Biological
Conservation 141: 2784–2794.
Landcare Research Page 40
Appendix 1: Explanation of key terms in this report
Kiwi taxa (plural) and taxon (singular): A taxon (plural taxa) is a ‘group of organisms of any
taxonomic rank (e.g. family, genus or species)’ (Concise Oxford dictionary of zoology1992).
Currently, the different ‘kinds’ of kiwi are not all taxonomically described in scientific
literature, and it is possible that some will be determined to be of lesser status than
subspecies. In practice, all are currently regarded as ‘conservation management units’ and
we call them ‘taxa’ here for simplicity’s sake.
Management regime: A kind of management such as trapping, aerial poisoning or ONE that
is applied to kiwi populations to increase their numbers.
Population growth rates: Kiwi populations are subject to annual change, depending on nett
outcomes of births and immigration versus deaths and emigration. We express change rates
in two ways, either as say 2% p.a. (so that each year the population is 2% larger) or for
modelling purposes as 1.02. That is, if the population is 500, then a year later it will be 1.02 x
500 = 510. Declines are expressed either with that word (e.g. a 2% decline), or for modelling
purposes as 0.98. With a 2% decline, a population of 500 will 1 year later be 0.98 x 500 =
490.
Modelling parameters: The population modelling in this report works by having (for each
taxon) a start population size and then a certain whole-population growth rate that derives
from how the kiwi in it are subject to different management regimes, each with different
growth rates. These numbers are the key parameters we use for modelling. For example,
Table 2 shows that for Fiordland tokoeka, there are 500 kiwi subject to the kohanga regime,
and these birds have a growth rate of 1.05 (the population increases by 5% p.a.). There are
550 kiwi subject to trapping, and they grow at 1.012 (1.2% p.a.). There are 100 that get aerial
1080 each 3 years, and these grow at 1.02 (2% p.a.). However, the vast majority of Fiordland
tokoeka (11400) have no pest management and their rate of change is 0.984 (i.e. on average,
a 1.6% decline p.a.). The overall taxon change rate after 1 year is 0.988 (a 1.2% decline)
because vastly more birds get no management than get some management. However, the
start population and these growth rates are only estimates, and may be wrong in some regard
– too low or too high. To allow for this possible error, we also model variations (e.g. ±30%)
on the best-guess initial population, and on each of the best-guess growth rates. These
variations are referred to in the report as parameter choices.
Conservation scenarios: Combinations of management regimes that in aggregate achieve a
desired growth rate (e.g. 2%) target. For example, our modelling suggests (Table 5) that you
can achieve a 2% increase for western browns either by subjecting more kiwi to aerial 1080
or more kiwi to trapping. All of the seven management regimes can be used to derive a large
number of different scenarios, that all have different outcomes for the kiwi population, and
different costs.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 41
Table 7 Key words used in this report. Note that examples of applications are in columns below the headings,
but that the table rows are not meaningful.
Kiwi taxa Management regimes
Example population growth rates
Example modelling parameter choices
Example conservation scenarios
Little spotted kiwi ONE 1.02 (i.e. a 2% increase per annum)
Best-guess initial population
Subject 800 kiwi to aerial 1080 instead of ‘do nothing’
Great spotted kiwi Kohanga or island marooning
0.98 (i.e. a 2% decline per annum)
Best-guess initial population minus 20%
Subject 500 kiwi to trapping rather than ‘do nothing’
Northland brown kiwi
Sustained trapping with occasional poisoning
1.016 (i.e. a 1.6% increase per annum)
Best-guess initial population plus 20%
Subject 500 kiwi to trapping and increase kohanga kiwi by 150 rather than do nothing
Coromandel brown kiwi
Aerial poisoning 0.985 (i.e. a 1.5% decline per annum)
Best-guess population growth rate under a management regime
Eastern brown kiwi Captive breeding Best-guess growth rate minus 30% (i.e. a low growth rate)
Western brown kiwi
Ground poisoning Best-guess growth rate plus 30% (i.e. a high growth rate)
Rowi ‘Do nothing’
Haast tokoeka
Rakiura tokoeka
Fiordland tokoeka
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 42 Landcare Research
Appendix 2: Cost data and assumptions
All data
The full list of data and their sources is available on request.
Administration
Communities reported on both funded and volunteered hours spent on administration (see
Time).
Advocacy
It is difficult to determine the effectiveness of advocacy due to its overlap with predator
control (Pierce & Westbrooke 2003).
Communities reported on both funded and volunteered hours spent on advocacy (see Time).
Furthermore, the reported data include total cost spent on advocacy resources. From added
notes, it became clear that these funds are used for ongoing expenses as well as capital, such
as signs. Since the shares of each could not be established, all these costs are treated as
capital (see Equipment capital cost). This implies that the estimate for this cost item is
conservative.
Automated acoustic recorders
Communities reported on time spent setting up and analysing data from acoustic recorders
(see Time).
The recorders were assumed to be the standard model developed by DOC. These were treated
as capital (see Equipment capital cost).
Benefits to non-kiwi species
Several cost items in this study, notably fences, benefit other native species as much as kiwi.
Without data on the presence and abundance of these other species, however, there is no
objective means of allocating the cost to them or kiwi. This study therefore disregards fence
depreciation and maintenance in estimating the costs of kiwi conservation.
Biosecurity
Only Northland communities reported a sum for biosecurity (protecting islands from pest
reinvasion). Based on expert judgement, this cost was not transferred to other taxa.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 43
Equipment capital cost
Equipment, such as quad bikes, 4×4s, traps, etc., is assumed to have a 10-year technical life,
so there is a depreciation cost of 10% per annum on the initial investment. It is assumed that
equipment was new at the start of the 15-year period, and that the depreciation costs start to
accumulate from the starting year.
The number of vehicles in Northland was converted to a per-hectare cost based on reported
area under management, which was then applied to other regions.
Communities reported primarily on the type and number of traps deployed. Prices found at
online vendors can be as low as NZ$ 10–15 for a Conibear trap (or similar) and as high as
NZ$185 for a Goodnature A24 trap. Where possible, a range of prices was used to produce a
low and a high cost estimate. In both cases, a further 15% bulk discount rate was applied to
allow for the possibility that online prices do not reflect actual prices.
For a low-cost estimate of bait stations, the model was assumed to be the Philproof Mini bait
station, whereas the high-cost model was assumed to be the Philproof Possum Large bait
station. A 15% bulk discount was applied to the lowest advertised price. Only Northland
communities reported on the sum of bait stations used. This was converted to the sum of
stations per hectare based on reported area under management, which was then applied to
other regions.
The impact of these sensitivity analyses around traps and bait stations on the overall costs for
conservation of each taxon is relatively minor, and in the final reporting averages are used.
Only Northland communities reported a number for other capital assets. The value of the
capital reported by the Tāwharanui Open Sanctuary was subtracted, because these assets
represent 98% of the total capital reported by Northland communities and therefore deemed
unrepresentative. The corrected capital value was converted to a per-hectare value based on
reported area under management, which was then applied to other regions.
Equipment operating cost
Only Northland communities reported on the costs of running their equipment. This was
converted to a per-hectare cost based on reported area under management, which was then
applied to other regions.
Fences
See Benefits to non-kiwi species.
Dog training
The effectiveness of dog training is a subject of debate (Dale et al. 2013), and cannot be seen
separately from wider advocacy activities.
Communities reported on funded and volunteer time spent on dog training (see Time).
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Page 44 Landcare Research
Landscape-level toxin campaigns (aerial 1080, ground-based 1080)
For this study, expert knowledge was used to incorporate bird distributions in calculations of
bird density. Bird density and numbers were used to approximate the area over which to
apply aerial poisoning operations.
In its report on the cost-effectiveness of aerial 1080, the Parliamentary Commissioner for the
Environment (PCE 2011) notes that the per-hectare cost of an aerial 1080 campaign is
between NZ$12 to NZ$16, with an additional NZ$ 1 per hectare cost for post-campaign
monitoring. Sporle (2008) suggests the cost of a 1080 campaign is NZ$17 per hectare.
In this report, a cost of $17 per hectare was used for aerial 1080 operations. If all transaction
costs (community engagement, planning, etc) are considered, the cost of aerial 1080
operations may be higher.
A cycle of one campaign every three years is assumed, except in the status quo and 0%
growth scenarios for great spotted.
For Rakiura tokoeka, the deployment of bait stations with 1080 was deemed more appropriate
than aerial distribution. DOC data suggests a cost of between $25 and $43. An average cost
of $30 was assumed as was a 3-year cycle.
Monitoring
Communities reported on both funded and volunteered hours spent on monitoring (see
Automated acoustic recorders and Time).
Operation Nest Egg (ONE)
For this conservation instrument, the reported cost per released juvenile was taken from
Gillies et al. (2013; Table 9 – Juvenile released). If taxons benefit from multiple ONE
facilities, the mean was taken. In the case of Northland brown kiwi, expert-based judgement
was used to determine an average cost for the ONE facilities concerned, which operate very
differently and have different costs per juvenile released.
Time
The conservation communities provided data on funded and volunteer hours. For this study,
funded hours are assumed to be contracted out to professionals, at a rate of NZ$ 30 per hour
for toxin application, trapping, animal control, administration and monitoring. This is in line
with guidelines for funding applications to Kiwis for kiwi.
Contracted hours for kiwi tracking dogs are valued at an hourly rate of NZ$45, as
recommended by guidelines for funding applications to Kiwis for kiwi. This rate was also
applied to contracted hours for dog kiwi aversion training.
Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth
Landcare Research Page 45
The value of volunteered hours is approximated by the median wage rate. The median hourly
earnings for New Zealand in 2014 is NZ$21.94 (Statistics NZ: New Zealand Income Survey
for June 2014).
We have not included activities that were clearly marked as DOC operations, but DOC staff
are likely to have higher hourly rates ($115 per hour has been suggested). For labour-
intensive conservation actions, the involvement of DOC staff rather than contractors and
volunteers will raise the cost of kiwi conservation by up to 3-5 times.
Toxins (ground-level application)
There is a large diversity of toxins for ground-level application, and each comes with its own
guidelines. Communities reported on the area collectively treated with toxins other than 1080
and brodifacoum, but the data did not allow explicit assessment of the use of each toxin.
Only Northland communities reported an expense for toxins that were not otherwise included
in the reporting template. This was converted to a per-hectare cost based on reported area
under management, which was then applied to other regions.
Only Northland communities reported the number of bait stations used. This was converted to
a per-hectare cost based on reported area ‘treated with other toxins’, which was then applied
to other regions.
Translocations
A full translocation consists of multiple steps, including time spent collecting suitable birds,
transport to and from islands, and transport across the mainland (although Air New Zealand
currently donates cargo space). The cost range depends on the level of involvement of DOC
staff (Hugh Robertson, 2014, pers. comm.) and was not included in light of the lack of
appropriate data.
Trapping
See Equipment capital cost and Time. The data are available upon request.
If communities did not specify the ‘other traps’ by type, the number of ‘other’ traps was
divided equally among the trap types reported (e.g., 50% Conibears, 50% DOC200s).