vol3 no1 birds special

eco-ark

From colour to camouflage

Illegal trade in birds

Climate change & birds

Understanding flight

Birds going native

Migration

plus ... News

Swan cultureBlue tits & exotica

Urban tree swallowsYour questions

Quiz & events

Volume 3 no.1Ark in the Sky

Birds special

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Ark in the Sky magazine is produced and published by imcic

Editor: Ita McCobbEditorial team:

Richard Casna, Jennifer Hope-Morley, Elizabeth Rigby, Thomas P Sawyer.Cover: Red-billed crane © Ark in the Sky.

Design & layout: imcicE-mail: [email protected]

Social media: Lisa StaffordWebsite: www.arkinthesky.org

Ark in the Sky, 3140 Rowan Place, John Smith Drive, Oxford Business Park South, Oxford, Oxfordshire.

Ark in the Sky is a registered charity no. 1148247

Here in the Northern hemisphere the cold nights and days are back again and it’s time to think about putting out food for the birds.

This got us thinking about how extraordinary birds are and we wondered what makes them such a successful life form. In this issue we investigate just that.

Birds are in fact one of the very few species to have not suffered the fate of the dinosaurs during the mass extinction event of prehistoric times. But how did they do it?

It seems that the answer lies in part in the fact that they lay eggs and that the constituents of the eggshells had evolved to a fairly sophisticated level by the time of the mass extinction event.

Evidently, the fact that they have feathers and can fly is also important to their survival but, surprisingly, so also is the shape of their feet and the way their blood circulation functions. (See pages 6-8 and 31)

But the attribute that differentiates the majority of birds is their ability to fly. We look at the principles of

flight and explain how these have been perfected by birds.

Birds have never been ones to stand still; like true survivors they are always on the lookout to better their environment. We explain the how, why and where of the annual migration undertaken by many birds.

Sadly during these long-distance migrations birds are at their most vulnerable and many become the victims of the illegal trade in birds. We investigate the main elements of this often horrific activity.

As with our site www.arkinthesky.org, throughout the magazine you’ll find news items and information from recently published reports.

Among the news we investigate are: The effect of urban activity on nestlings; The effect of climate change on bird life; How great tits and blue tits are finding it hard to breed in parks that are planted with exotic trees and How scientists have discovered that large-brained birds may be intellectually comparable to apes!

Ita McCobb

Image facing – Oeufs-fixés, Adolphe Millot – Nouveau Larousse Illustré (Eggs not in proportion to each other.)

1. Buzzard2. Falcon3. Sparrow hawk4. Blackbird5. Thrush6. Rook7. Corn bunting8. Hawfinch9. Sparrow10. Chaffinch11. Pipit12. Reed bunting13. Cuckoo14. Hummingbird15. Crossbill16. Wren17. Nuthatch18. Nightingale19. Goldcrest20. Hedge sparrow21. Rock bunting22. Reed warbler23. Sedge warbler24. Warbler25. Blue tit26. Tree warbler27. Waxwing28. Oriole29. Jacana30. Grouse31. Ptarmigan32. Pheasant33. Partridge34. Quail35. Avocet36. Spotted redshank37. Dotterel38. Virginia plover39. Lapwing40. Green sandpiper41. Tern42. Common tern43. Ruppell’s tern44. Seagull45. Loon46. Guillemot47. Great auk48. Puffin49. Puffin50. Grebe51. Emyde52. Mauritanian tortoise53. Catshark (mermaid’s purse)54. Catshark (mermaid’s purse)55. Shark56. Chimaera57. Lamprey58. Cuttlefish59. Arctia60. Geometer moth61. Geometer moth species62. Clouded yellow butterfly63. Diloba moth64. Lampoon65. Wall brown butterfly66. Laphygma moth67. Acosmetia moth68. Ennemos moth69. Attacus moth70. White admiral butterfly71. Bryophile moth72. Catarhoe moth.

Birds – always extraordinary!

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Eggs page 2

Editor’s message 3

From colour to camouflage 6

Understanding flight 9

Flightless birds 12

Migration 13

Chicks drowned out 16

Climate change & birds 17

contents

From colour to camouflage: Delta-wing function of webbed feet gives hydrodynamic lift for swimming propulsion in birds, Johansson LC, Norberg RA, Nature, 3 July 2003; Oxford English Dictionary, Oxford University Press; National Audubon Society; RSPB; Sibley and Monroe’s world list of birds; www.arkinthesky.org; Cornell University Ornithology Laboratory; Northwest University; Patuxent Wildlife Research Center; Prey taken by the Barn Owl in England and Wales, D.E. Glue, Royal Holloway College Zoology Dept, University of London published by Informa Ltd. Understanding flight: Sibley and Monroe’s world list of birds; Cornell University Ornithology Laboratory; V formation in bird flight, Lissaman and Shollenberger, 1970; Northwest University; Patuxent Wildlife Research Center; Stanford University Ornithology Department; Flight briefing for pilots 1, N H Birch and A E Bramson, Pitman.Flightless birds: The encyclopedia of New Zealand, New Zealand Government; Cognitive adaptations of social bonding in birds, Nathan J Emery et al., The Royal Society; Stanford University Ornithology Department. Migration: Oxford English Dictionary, Oxford University Press; National Audubon Society; RSPB; British Trust for Ornithology; Movements of banded Arctic waders to and from New Zealand, Adrian C. Riegen, Notornis 1999; Sibley and Monroe’s world list of birds; The encyclopedia of New Zealand,

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New Zealand Government. Drowned out: Acoustical Society of America (ASA); Dalhousie University Halifax, Nova Scotia. Climate change & birds: RSPB; British Ornithologists’ Union; BTO; onlinelibrary.wiley.com; Department of Conservation, New Zealand Government. Birds going native: RSPB Royal Society for the Protection of Birds; British Ornithologists Union (BOU); British Trust for Ornithology (BTO); GB Non-native Species Secretariat (NNSS); The encyclopedia of New Zealand, New Zealand Government. Illegal trade in birds: UNEP (United Nations Environment Programme) and CMS (Convention on the Conservation of Migratory Species); Born Free USA; IUCN Red List; Birdlife International; European Parliament; Bern Convention. Blue tits & exotica: Anglia Ruskin University; Cambridge University Botanic Garden. Swan culture: RSPB; British Trust for Ornithology; Cognitive adaptations of social bonding in birds, Nathan J Emery et al., The Royal Society; Sibley and Monroe’s world list of birds; The Regal Swan Foundation. Blogit birds’ eggs: Egg shape changes at the theropod–bird transition, and a morphometric study of amniote eggs, D. Charles Deeming, Marcello Ruta, Royal Society Open Journal, 5 November 2014. Feed the birds: RSPB; Patuxent Wildlife Research Center; Cornell University; US National Bird-Feeding Society.

contents continued

Quiz 20

Birds going native 22

Illegal trade in birds 25

Blue tits & exotica 28

Swan culture 29

Blogit 30

Events 31

Feed the birds 32R

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Why has man always envied birds? They have feathers and strange feet, but these (often) very tiny creatures also have a surprisingly long list of talents – including

(in most cases) the physical ability to fly.

There are over 9,700 recognized bird species consisting of 204 different bird families.

Modern birds fall into two main categories: Passerine (from the Latin “passer” meaning “sparrow”) and non-passerine.

Passerine birds make up the largest category of birds and are distinguished by having feet adapted for perching – that is, they have three toes pointing forward and one pointing backward. This category includes all songbirds.

Non-passerine birds are non-perching birds. This category includes pigeons, ostriches, waterfowl, game birds, woodpeckers, hummingbirds and kingfishers.

FeetBirds’ legs and feet are as important as their feathers in supporting their varied abilities. Birds walk on their toes as opposed to their whole foot. Most bones of a bird’s foot, other than their toes, are fused to each other.

The legs and feet of many ducks and birds are important in maintaining body temperature. Their feet provide not only balance and mobility when swimming, walking, flying or diving, they also act as natural heating elements. These birds’ legs and feet have a special heat-exchange system known as “counter-current flow” where the arteries and veins in the legs are positioned closely to each other in order to maintain heat in the legs and feet.


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from colour ...

from colour ...

to camouflageSwimming birds such as coots, cormorants, ducks, gannets, geese, grebes, herons, pelicans, plovers, sandpipers and swans have webbed feet, which help them to both swim in water and walk with stability on land.

When swimming these birds sweep their webbed feet backwards in a curved path aligned with the direction in which they are swimming. Because of their shape, webbed feet can generate strong, continuous propulsion.

FeathersBird feathers, generally known as “plumage”, fulfil a wide variety of purposes; mainly, flight, courtship and insulation and waterproofing against the weather.

A bird’s plumage weighs overall heavier than any other part of its body.

Feathers are made out of keratin (the same as our hair and nails) and come in a variety of shapes and sizes depending on their uses.

Contour feathers are the outermost feathers – creating the overall shape of the bird.

Remige feathers are the largest contour feathers (often the large flight feathers) and are attached by ligaments or directly to the bone.

Rectrice feathers are the tail feathers used to provide stability and control.

Covert feathers are rows of feathers that help streamline the shape of the wings and tail and help insulate the bird.

After feathers resemble the main feathers and provide an extra layer of warmth – generally found in more abundance on flightless birds.

Bristles are small contour feathers which lack barbs on the outermost part and have an especially stiff rachis (shaft/spine). Rictal bristles that project from the beak are believed to provide protection for the bird’s eyes.

Down feathers have minimal or no shafts or

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hooks, hence are very soft fluffy feathers that create insulating pockets of air.

Semiplume feathers are found between other feathers providing an additional layer of warmth and ensuring a streamlined shape.

Filoplume feathers are relatively stiff and hair-like feathers that are thought to provide the bird with feedback on contour feather activity.

Powderdown feathers are found in just a few birds such as herons. These feathers are never moulted but grow continuously, eventually disintegrating at the tips to form a fine powder that drifts into the other feathers. It is possible that this then provides the bird with an extra layer of waterproofing.

Feathers are generally attached to a bird’s body in lines – these lines are called “pterylae”. The spaces on the bird’s body without feather tracts are called “apteria”. As with most animals, the densest area of feathers is to be found on the bird’s head and neck.

Feather shapes play an important role in controlling flight – in particular the shape of tail and wing feathers, which provide “lift” at take-off and during flight.

The top and underside feathers are often of a different colour in order to provide camouflage when a bird is in flight.

The condition and quality of a bird’s feathers are important when attracting a mate – the theory being that brighter healthy-looking plumage is more likely to belong to a healthy bird, which is not only attractive but also more likely to be a better bet as a potential partner.

Plumage is also used in the bird world as camouflage to provide protection. During the winter snows the Willow Ptarmigan changes its plumage to white to match the snow-covered ground and in the spring these feathers moult and the new feathers are mottled brown – maintaining the bird’s camouflage.

FeedingBirds have to eat several times a day in order to survive. In winter, birds have to eat enough every day to make it through a cold night. Just two days of bitter cold and ice can kill.

By daybreak their energy supply (which is what

helps to keep them warm) is running out so they have to eat as soon as possible.

In order to compensate for loss in body temperature they can also lower their metabolic rate (the rate their bodies consume energy).

Most birds feed on the supply of food found in their natural habitat. Garden birds such as robins, blackbirds and sparrows eat seeds, worms and insects whereas waterside birds such as cormorants and gulls feed mostly on fish and plankton and aerial birds such as swifts and swallows like to catch their insects in flight.

Birds need less water than mammals although many small birds need to drink at least twice a day. Because seed-eating birds have a dry diet they need to drink regularly whereas insect-eating birds get much of their water from their food while species such as swallows and swifts scoop up water from rivers and lakes – while still in flight!

Singing birdsBirds sing because their vocal organ (called a syrinx, which means “Pan pipe”– from the Greek word “surinx” for “pipe”) is able to produce sound. Their syrinx is located at the base of their trachea (windpipe).

Sound is produced by vibrating air as it rushes past the membranes of the walls of the syrinx and its surrounding air sac. The fluctuations created control the airflow and hence the sound. Pitch is controlled by the tension on these membranes and both pitch and volume by the force of the air passing through them. Amazingly, birds can control both sides of their trachea independently, which is why some are able to produce two notes at once!

Speaking birdsSome birds are natural mimics. Most notable are budgerigars, crows and parrots. They can do this because their syrinx is located where their trachea branches off into their lungs.

Some birds can mimic human speech, even stringing together complete sentences, while others know only a few unrelated words. Many budgerigars have been known to have a vocabulary of over 2,000 words!


To find out more visit: www.arkinthesky.org/en/discover/birds


Flight

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The attribute that differentiates the

majority of birds is their ability to fly. It is their unique combination of

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UNDERSTANDING


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Birds use their ability to fly not only to help them move speedily from place to place but also to help them feed, for courtship displays and to avoid possible predators. There are a few birds that cannot fly.

Principles of flightTo appreciate what an amazing ability flight is, it is useful to understand the four basic principles of flight, which need to be kept in constant balance to achieve successful flight.

Lift: Lift is what keeps an object in the air. Birds fly because of the lift obtained from their wings. This is provided for the most part by the shape of the wings and wing surfaces.

Efficient lift is achieved because the aerofoil section of the wing forces the air passing over the upper surface to travel further than that passing below it. This air has a greater distance to travel than the air below but, with no more time in which to do so it is forced to travel faster. As a result air pressure above the wing is reduced and lift is achieved.

To control lift two factors are used – airspeed and the angle of the wings (called “the angle of attack”). The faster you fly through the air the more lift you achieve. But you need to slow down occasionally. To do this you need to be able to reduce the angle of the wings. Conversely, when you reduce speed you need to increase the angle of the wings.

This all makes sense until you achieve that critical angle at which the streamlined flow of air over the wings’ upper surface is forced to change direction too abruptly to be able to continue to follow the curvature of the wing – this is called a “stall”. This abrupt change of

airflow takes away the lift that holds the plane in the air and the plane begins to lose altitude and can get into a spin. This is something you may have seen sea and water birds using to great effect when diving to catch their prey.

All birds that can fly are aerodynamically shaped. Their bodies are streamlined to help overcome air-resistance. Their wing feathers are specifically formed and structured to enable flight. They have a special shoulder mechanism, which enables their wings to produce the swift and powerful upstrokes necessary for lift, particularly when taking off or at very low speeds.

Birds change the angle of attack between the up-stroke and the down-stroke of their wings – at the down-stroke the angle of attack is increased and decreased on the up-stroke.

Drag: However streamlined your aircraft’s design there are bound to be elements that reduce its aerodynamics, which result in resistance that slows it down as it passes through the air.

Drag exists in two main forms: induced drag and profile drag. In a bird these forces of drag create resistance as it passes through the air. Induced drag is caused by the inequality of airflow pressures above and below the bird’s wings and body. Profile drag is caused by the often heavy-keeled frontal area of a bird and sometimes its feet, which protrusions interfere with the streamlining of its shape slowing it down.

Thrust: Thrust is the force that compels a flying object to move forward through the air. In a plane it is produced by the engine acting through the propeller. In normal level flight thrust and drag must be in balance for the airspeed to remain constant. Thrust is absent when an aircraft or bird is gliding.

A bird creates thrust when it flaps its wings, which action moves it forward through the air. At each up-stroke the wing is folded slightly inward to conserve energy.

Bird skeletal breastbones have adapted into a protruding keel, suitable for the attachment of the large, powerful muscles needed to provide the energy for flight. Added to which, the vanes of each feather incorporate hooks called “barbules” that act like a zip to hold the


Most wing types fit into one of four categories:

Elliptical-shaped wings are perfectly designed for short bursts of high speed and tight manoeuvring in confined spaces. Birds that have this wing type include crows, blackbirds, sparrows and gamebirds (that need to take off quickly).

•High-speed wings are short, pointed wings that when combined with a heavy wing weight and rapid wing movement produce high-energy, extreme speeds most notably in peregrine falcons, swifts and ducks.

•Passive soaring winged birds have long primary wing feathers that fan outward at the tips to create “slots” that allow these birds to rise extremely high in the air on thermal currents. Typical are eagles, hawks, pelicans and storks.

•Active-soaring wings are long and narrow and allow these birds to soar and glide for long periods and at slower speeds. Slower speeds are essential to birds that dive for fish.

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feathers together, giving them the strength to maintain an aerofoil shape.

When gliding, birds achieve both a vertical and a forward thrust generated by either descending or by gliding on a “thermal”.

Weight: As opposed to lift, which acts vertically upward, weight acts vertically downward. Birds have evolved in a way that virtually counteracts this problem. A bird’s skeleton is hollow and contains hundreds of air sacs. This keeps its weight to an absolute minimum.

In order to keep weight to a minimum, bird skeletons have done away with many unnecessary bones. This said you will still see some heavy birds flying in a nose-up attitude!

Wings and wing shape

HoveringMost birds that hover are small with active-soaring wings. Hovering demands a lot of energy and is achieved by generating lift through the frenetic flapping of wings.

Although large birds can hover for short periods they do so by flying into a headwind, which allows them to remain seemingly stationary (relative to the ground beneath them).

Formation flyingWe’ve all seen flocks of birds flying in a V formation Formation flying is a highly organized group activity, which has evolved in order to save energy, especially on long-distance flights.

This energy saving is achieved in two ways: firstly by the lead and trailing birds regularly changing position with other flock members and secondly by the fact that the physical formation actually reduces overall drag.

A 1970 study by Lissaman and Shollenberger showed that each bird in a V formation can reduce drag by up to 65% and as a result increase their range by an amazing 71%.

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The emu’s tale

According to Cornell University Ornithology Laboratory, the flightless Emu of Australia has specially adapted after-feathers that are as large as its main feathers and provide protection as the bird moves through the thick brush of its natural habitat.

Relatively recent additions to the Emu’s normal range are four-foot high sheep fences topped with barbed wire. Seemingly unperturbed, the flightless Emu crosses these fences by running straight at them, resulting in a high-speed somersault over the fence!

“The tuft of feathers left behind is a sure indication of an Emu crossing and a testament to the amount of protection the feathers offer,” says the lab spokesman.

There are around 40 species of flightless birds – they include the ostrich, emu, cassowary, rhea and kiwi

and of course penguins.

Flightlessness is believed to be due to some birds having become very secure in their local environment and so not having the need to fly. It has resulted – over several generations – in their losing the physical anatomy necessary for flight.

Often these birds have evolved over the centuries on landmasses that have become islands. In this relative isolation and without the immediate threat of other large animals or man, these birds’ ancestors found it unnecessary to fly and eventually their ability to do so became unnecessary.

As opposed to birds that can fly, flightless birds have smaller wing bones and minimal keels on their breastbone. In order to keep warm, they also have more feathers than flying birds – particularly after-feathers.

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Bird migrationThe mass annual movement of birds between their Summer breeding grounds

and their Winter roosts in search of warmth and food is a perfectly logical way to ensure the survival of the species

– but en route they often encounter many dangers and obstacles.

Around 4,000 bird species migrate and a few, such as partridges, never ever travel out of their local environment! The birds we notice migrating are the large flocks of birds such as starlings and cormorants as they roost together preparing for their annual migration. But smaller birds such as swallows and finches are the unexpected masters of this activity.

Birds migrate for three main reasons: to find more abundant food sources, to find warmth and to find suitable nesting grounds.

In the Spring birds migrate to take advantage of the annual abundance of insect populations, plants and suitable nesting locations in warmer climes. They make their return journey at the onset of Winter, as plant life and hence the profusion of food sources diminish with the lower temperatures. This also coincides with the fact that their offspring have hatched and

grown sufficiently independent to be able to make the often long flight to their warmer winter quarters where they are likely to find a more prolific supply of food.

Before we get confused it is worth reminding ourselves that the equator is the warmest place on Earth and the further away you go from the equator in both a northerly or southerly direction the colder the temperature becomes. So if they live in the Northern hemisphere birds will be flying south in Winter to find warmth and if they live in the Southern hemisphere they will fly north in Winter to find warmth.

Types of migrationThere are three main types of migration undertaken by birds:

Local migration: Short distance migration (sometimes called “altitude migration”) is

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undertaken by birds that simply move down to lower altitudes to find food at the onset of Winter. Typical of these birds are skylarks and meadow pipits.

Medium-distance migration: This is a country-hopping style of migration that is generally undertaken by birds such as snowy owls, blackcaps, white throats, yellow wagtails and many species of starling, all looking for more secure nesting places and a more plentiful supply of food. Several Winter seabirds, such as puffins and gannets, migrate inland in Spring to breed having spent the Winter out at sea.

Long-distance migration: This involves a change of hemisphere and demands very long distance flight and exceptional stamina on the part of the birds undertaking it. Long-distance migratory birds include falcons, particularly the peregrine falcon, geese and storks, although many small birds such as cuckoos, swallows, swifts, nightjars, ospreys and terns also make these hazardous journeys.

Temporary migrations are:

Passage migration: This is when birds make a “pit-stop” in a country they are passing over and stay for a few weeks to rebuild their stamina and energy levels before continuing their migratory route. Typical are terns.

Partial migration: Some members of a species will migrate whereas others do not. Eastern European starlings, for example, migrate to the climatically milder UK in Winter whereas their UK-born counterparts stay in the UK throughout the year.

Moult migration: Every year birds shed their feathers as new feathers grow – this can be a very vulnerable time for birds. This is especially problematic for wildfowl that lose their flight feathers when they moult. These birds moult migrate to safer localities to moult. Once their new feathers have grown they return or continue their migration.

Typical examples are wood sandpipers that stop for a partial moult en route when migrating and the famous shelduck that flies to either the island of the Helgoland Bight or (in smaller numbers) to Bridgwater Bay in Somerset for their moult.

When to migrate?A hormonal Springtime reaction, preparing the bird for courtship and mating, warns the bird that it is time to leave to find a suitable breeding environment. This reaction is probably triggered by temperature changes in local environment and the number of daylight hours available in which to feed.

To prepare for migration a bird will eat vast amounts of food to build up its energy sufficiently to survive the journey. The food is stored as fat, which its body then converts into the extra energy used during the flight.

Changes in atmospheric pressure are the key to knowing when to set off. High pressure usually means the perfect weather in which to start a migration. Low pressure brings cloud, rain and wind – in which case the birds will wait until the weather is more clement.

In certain species, particularly wading birds, the males, females and even the younger birds migrate in separate groups leaving (and arriving) at different times.

NavigationMigrating birds can cover thousands of miles, navigating by following landmarks such as mountains, rivers and coastlines. Research has also shown that birds navigate by the Sun (or Moon and stars in the case of night flyers) as well as changes in the Earth’s magnetic field, temperature, wind speed and even smell.

Specific routes have evolved over generations, mainly because of the number of suitable food stops they will find en route.

Birds have an inbred navigational instinct which allows them to follow the same migratory course year after year.

Loop migrationWhile most migrating flocks follow the same route for their return as for their outward journey, there are some that use what is known as “loop migration”and follow a different path for their return. This is believed to be because of seasonal climatic differences during their migration. To avoid this problem the birds historically fly the route that provides the most food and shelter.


Large masses of water can create a problem. While birds with enough energy to cross will do so, others will make an overland detour to feed and wait for suitable winds and thermal currents. Others, such as many wading birds, prefer to follow coastline routes where they can feed in river estuaries.

•In September each year, eastern bar-tailed godwits (see above) cross the central Pacific to New Zealand from Alaska. Unlike seabirds they cannot rest on water or feed at sea, making this 11,000 kilometre journey the longest non-stop flight undertaken by any bird. Their return to Alaska is taken in stages stopping off in Australia, Japan and/or China and Russia to arrive in Alaska to breed in May.

•Conversely, for its migration to the breeding fields, the seemingly lazy cuckoo parent will actually put all its energy into taking the direct route – flying long distances over water where, being a land feeder, it cannot feed. It makes you wonder if this is why cuckoos lay their eggs in other birds’ nests – perhaps they are so exhausted they really don’t have any energy left to care for their offspring!

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When undertaking their migration, birds regularly encounter obstacles along the way. Some of these are natural obstacles such as mountains, oceans, seas, extreme weather conditions and of course predators (often other larger birds) looking to take advantage of weak and tired migratory birds.

•Other obstacles are man-made, such as extremely high buildings and towers, lighthouses, oil and gas rig flares, radio and television masts, power lines and wind turbine blades – the list goes on.

•Structures such as wind turbines are naturally positioned in areas where wind and air currents pass unhindered. Sadly, these are the migratory routes of birds and great flocks of migrating birds have been wiped out by the giant turbine propellers. Wind turbine operators are beginning to construct bird radar warning stations that switch off the propellers when flocks of birds approach.

•Migratory birds can become disorientated or get lost, which means they often succumb to predators or hunters or simply die from exhaustion.

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Drowned out!

Traffic noise, construction and other human activities may be making it harder for chicks to hear their parents.

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This rapid response increases their chances of getting a good meal – but it also puts them at risk of misidentifying predators as parents.

The researchers tested their theory on baby tree swallows (Tachycineta bicolor) and compared the chicks’ responses to sounds played with and without background noise.

They found that background noise reduced the chicks’ responsiveness to both feeding calls and alarm calls. The chicks often didn’t beg when responding to feeding calls but continued to beg (instead of taking cover and falling silent) when the parents warned of predators.

According to researcher Andy Horn, human activity could be breaking the vital line of communication between parent and chick. He emphasized that, “We usually associate declines in animal populations with our physical destruction of habitat, but the noise we make is another threat that we can’t ignore.”To find out more visit: www.arkinthesky.org/en/discover/birds

Research by Dalhousie University in Halifax, Nova Scotia suggests that the sound of urban environments could be drowning out the vital vocal calls of parent birds and therefore threatening the survival of their young.

As nestlings are vulnerable and unable to fly from their nests they depend on their parents for both food and protection from predators.

Vocal communication between parents and offspring helps young birds to determine when they should beg for food and when they should remain silent to avoid detection by a predator searching for a tasty meal.

Noise also drowns out the chirping of hungry chicks, leaving their parents oblivious to the needs of their young.

Faced with tough competition from hungry siblings, chicks instinctively react to any sign that a parent might have food, vigorously begging to attract attention.


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Birds & climate change

Climate variability and change affects birdlife in a number of ways. It is predicted that more bird species will lose than gain from these projected changes.

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Climate change is likely to add to the already existing pressures on bird populations around the world and increase the risk of extinction for many species.

Without dynamic and immediate action to reduce climate change it is predicted that the future range of the average European bird species will shift northeast and will reduce in the size compared to its normal range.

Specific groups of birds are at higher risk from climate change, in particular migratory birds, mountain birds, island birds, wetland birds, Arctic and Antarctic birds and seabirds.

Bird species that can move easily to new habitats are predicted to be less affected, for example the hoopoe, a bird found in southern Europe that has reached northern France.

However, those that have a narrow environmental range are expected to decline, for example the red-necked phalarope, once found on mainland Scotland and the Isles, is now almost entirely limited to the northern parts of Shetland.

This shift in distribution may mean that birds face new competitors, predators, prey and diseases to which they are not adapted.

Where local and regional climates tend to warm, bird species are expected to shift their distributions either towards the poles or upwards in elevation in order to help maintain their optimal temperature range.

Species unable to extend their geographical range could face extinction. This includes those with ranges in Scotland or in mountain regions – such as the snow bunting, which today survives only on the Cairngorm plateau. The Scottish crossbill, the only bird species unique to the British Isles, is also likely to suffer.

Breeding One of the most widespread effects of climate change has been changes in the timing (phenology) of biological events. Birds are

nesting earlier, a pattern seen around the world supported by significant trends for earlier nesting associated with global warming.

Although many birds are breeding earlier in the season, there are others that are breeding too late to hatch their young when their food supply is at its optimum.

Migration In response to the rise in temperatures the arrival and departure of many migratory species have changed. Swallows and martins arrive earlier in the UK, an event seen in many migratory bird populations across Europe.

In some locations however, climate change is causing individuals of some species to no

longer migrate as they have found the climate suitable year round. Some bird species no longer winter in Spain, France or in the north of Africa. For example, cranes, which normally migrate to Spain and Portugal, stay in Germany.

The fact that some species no longer migrate has had a

severe impact on their numbers. If there is a hard winter, most will not survive it.

Increased storm frequency, lower water tables, higher drought frequency, sea level rise and habitat shifts resulting from climate change can all have a huge impact on migratory birds.

Migratory birds will be forced to change their migration routes or the places they breed or spend Winter, although there is concern that many migratory species will be unable to adapt. Many will struggle to find sustenance for long migrations particularly because of industrialization and drought.

Sources of foodClimate change also impacts on prey abundance, causing a mismatch between the timing of food availability and the time of greatest need for birds rearing chicks.

It has been reported that this change has

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caused reduced breeding success for the pied flycatchers and great tits in the Netherlands.

The impact of climate change on insect life has shown that some of these species cannot migrate fast enough to keep up with global warming, which suggests that birds that feed on insects could face problems finding food as they migrate north.

A lack of food as well as nesting sites has contributed to dramatically lower numbers of species, including the turtledove, cuckoo and nightingale.

Saltwater inundation caused by tidal surges damage freshwater habitats, killing fish and thus affecting the birds that feed on them.

Increasing sea temperatures have led to the shift northward of the distribution and abundance of fish species. Around the UK the abundance of sand eels, a key prey for kittiwakes, auks and terns, has been reduced leading to a decline in the breeding success at a number of breeding colonies in eastern Britain.

Climate change adaptation and mitigation Climate change adaptation and mitigation actions can cause unintended problems for many bird species (i.e. the impact of onshore wind farms on white-tailed eagles in Norway and offshore wind farms on whopper swans) but they can create an opportunity for conservation if deployed carefully (there is evidence that coppicing and thinning can increase bird habitats).

Habitat loss and fragmentation are seen as the greatest threats to birdlife; however, it seems that if climate change continues unrestricted, it is this that will cause greater rates of extinction among birds. The key threat being the rate at which climate change is occurring, which leaves little time for species to adapt.

James Pearce-Higgins of the BTO and co-author of Birds and Climate Change said, “We have a window of opportunity to reduce the threat that climate change poses if action is taken now. The challenge for policymakers is to ensure that renewable energy and other measures to reduce climate change are adopted without adding to the threat that many birds face.”


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Can you name these birds?

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You’ll find all the answers in this magazine or at: www.arkinthesky.org/discover/birds

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Birds going native

Most non-native species (sometimes known as “aliens”) do not have problems adapting to new locations in different ecosystems. While they often adapt without causing disruption to the local environment or native bird life, a minority is deemed “invasive” as they have a negative impact on local wildlife, habitats or economy.

Those bird species that are considered invasive in one region may not be harmful in a different region and are therefore simply considered as non-native.

The separation of regions of the world by physical barriers such as oceans, mountain ranges and deserts, which stop different ecosystems and ecological communities mixing, has allowed a huge number of living bird species to exist.

However, with the movement of species around the world, these geographical barriers have been opened up allowing non-native species to establish and often flourish, free from native predators, pathogens (viruses) and competitors.

The introduction of non-native bird species is rising sharply due to the increase in trade, transport, travel and tourism. Worldwide globalization has offered new routes and increased opportunities for non-native bird species to establish in new areas. The adaptable Myna bird, for instance, is considered invasive in both Australia and South Africa and it is on the IUCN list of worst invasive species.

Birds that “go native” are non-native bird species that have been introduced into areas outside their natural range by humans,

either deliberately or accidentally.

There are several ways that non-native bird species can invade different regions, both naturally and with human assistance.

Deliberate importBird species may be imported deliberately for various reasons, which can have disastrous consequences. The house sparrow and European starling, for instance, is considered invasive in the US. Apparently the starling was introduced into New York’s Central Park in 1890 as part of a plan to introduce all the birds mentioned in Shakespeare’s writings!

The rainbow lorikeet is native to some parts of Australia and was imported into New Zealand in the 1990s. A dominant and prolific bird, it now poses a significant threat to native New Zealand wildlife.

Geographic expansion Birds that expand their habitat due to habitat loss or are designated a protected species may be considered invasive if their expansion is damaging to other species or ecosystems.

An example is the cormorant, which is a protected species in Europe but is beginning to proliferate so that flocks are threatening the food supplies of other waterfowl and local fishermen’s livelihoods.

Escape from captivity Birds that are kept as pets and those that escape from farms or contained breeding grounds may establish wild populations that can impact on resident birds, for example, the parrot colonies now appearing in many major cities.

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Accidental import Some bird species may be introduced to new habitats inadvertently by aircraft or ships. Often, however, they are unable to establish a wild population due to lack of breeding partners.

Climate change Climate change might easily make Britain and other countries in the Northern hemisphere more suitable for a wide range of non-native bird species, in particular migratory birds that arrive for the Summer breeding season, but stay on given the warmer Winters!

Threats from non-native birds

As well as being a threat to biodiversity, damaging economic interests such as agriculture, forestry and fisheries, invasive non-native bird species can cause problems for native birds in the following ways:

Competition for resourcesIntroduced species compete with native species for resources like nesting sites, food and space.

Disruption of prey balance New predators can have disastrous effects on native birds particularly on islands and freshwater habitats where birds have evolved in the absence of predators and are not able to adapt quickly enough.

HybridizationSome non-native species have been able to breed with another related but distinct species, thereby creating hybrids. Over time, the unique genetic diversity of one species can be lost and a native species can become extinct.

Introduction and transmission of new parasites or diseases

Any new parasite or disease carried by non-native species can be a serious problem for native birds, as they will not have developed immunity.


Illegal trade in birds

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There are two types of trade in wild birds. Firstly, the capture and trade of exotic and highly intelligent birds to sell as pets and secondly the illegal killing, taking and trading of migratory birds. continued over g


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There are two main types of trade in birds. Firstly, the capture and trade of exotic and highly intelligent wild birds to sell as pets, often to be displayed as “trophy possessions” in private zoos, and secondly (as if the challenges that birds face during their often long migration wasn’t enough) the illegal killing, taking and trading of migratory birds.

The popularity of exotic birds fuels the bird trade around the world. The impact of the pet trade on wild parrot populations has been devastating, resulting in nearly one-third of the world’s 330 parrot species facing extinction.

According to the IUCN Red List, the numbers of most parrot species are in serious decline around the world.

Exotic birds are not considered domestic animals (even when they have been bred in captivity) and it is simply cruel to cage them as this results in stress and often anti-social behaviour, depriving them, as it does, of their normal, inbred behavioural patterns.

Pet bird owners often quickly become bored with their birds and a huge number of these birds are neglected or simply ignored so they often starve to death. Some of these birds are released to fend for themselves. But since most of them will find themselves in a totally alien environment they generally do not survive.

While legislation can help control these abuses there is only one sure way to stop this trade and that is for everyone to refuse to buy such birds. We should remember that birds were meant to be free in their natural habitat and not to be kept in confined spaces – we wouldn’t like it.

Directive 2009/147/EC of the European Parliament and of the Council of 30 November 2009 on the Conservation of Wild Birds identifies 194 bird species and subspecies as particularly threatened and in need of special conservation measures. The Directive is looking to implement far-reaching measures for the protection for all of Europe’s wild birds.


ILLEGAL TRADE IN BIRDS


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Around 4,000 bird species migrate worldwide. This includes many different species of bird, from large to small and from exotic to seemingly communal garden varieties.

The problems faced by migratory birds were specifically addressed at the 6 November 2014 UNEP (United Nations Environment Programme) and CMS (Convention of Migratory Species) conference in Quito, Ecuador.

The conference found that the intensive unsustainable hunting and the illegal killing of migratory birds are driving species to the brink of extinction. Protected birds such as the spoon-billed sandpiper and the yellow-breasted bunting are globally threatened.

A key measure proposed is the creation of an intergovernmental task force to address these problems. CMS Executive Secretary Bradnee Chambers called this a much-needed measure to prevent global wildlife crime and help ensure the survival of many endangered bird species.

Egypt and Libya have already developed an action plan to put an end to the practice of trapping migrant songbirds. Trapping has intensified so much so that there is now a 700km line of nylon nets set up along the Mediterranean coastline of North Africa to trap these birds!

BirdLife International is currently assessing the scale of illegal killing of birds in the Mediterranean region. First results suggest that tens of millions of birds may be being illegally killed each year. Huge numbers of migratory birds are killed in Malta every year – including many species protected by international law.

Numbers of the semi-palmated sandpiper have plummeted by almost 80% over the last 30 years. The birds are killed with a method called a “chocking wire”. As the birds pass, the wire is whipped up and down, killing or injuring passing birds in the flock.

Migratory bird killing

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ILLEGAL TRADE IN BIRDS


Great tits and blue tits are finding it hard to breed in parks that are planted with exotic trees

and shrubs.

A study by Anglia Ruskin University and the Centre for Ecology and Hydrology scientists compared the success of birds breeding in nest boxes in city parks to those breeding in nest boxes in traditional woodland and hedgerows.

The energy expended by breeding adults was also monitored and it was found that they had lower breeding success despite working harder than their country cousins.

The larger physical gaps in the tree canopy caused by the distances between trees in parks compared to woodland and also the presence of exotic plants and trees, which do not support as much of the insect food the birds eat and need to feed their chicks, adversely affected breeding success.

It appears that exotic trees and plants represent a greater challenge for the birds than locations with no trees at all as the birds expend energy and time searching for food among them with little reward for their effort.

Dr Harrison said: “Our research has shown how difficult it is for insectivorous birds like blue tits and great tits to breed in urban parks full of exotic trees and shrubs.”

“The birds in our cities live longer because we feed them, but they struggle to breed and raise fewer chicks,” she added. “As a result more of the birds breeding in Cambridge are older, mature individuals.”

“Our research shows that even very small spaces can become hotspots for birds, but for an urban habitat to support wild birds we need to protect our mature, native trees, limit the number of exotic species that are planted and not insist on keeping gardens perfectly manicured.”

Blue tits & exotica

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www.arkinthesky.org 29To find out more visit: www.arkinthesky.org/en/discover/birds

Swans are the largest members of the Anatidae (waterfowl) family that includes ducks and geese.

Swans are among the largest flying birds.

There are seven species of swan (Cygnini), Australian black swans, Bewick swans, English mute swans, North American trumpeter swans, North American tundra swans, South American black-necked swans, South American swans (coscoroba and whooper swans).

Swans in the Northern hemisphere are pure white whereas those in the southern hemisphere are a mixture of black and white.

Scientists believe that large-brained birds like swans may be intellectually comparable to apes. Scientists say that such bird partnerships resemble those of dolphins and primates.

Bird society in general is controlled by the need to preserve the species. To this end, swans tend to flock together in secure environments during the Winter months, then, when the breeding season arrives, they form mating pairs.

The majority of swans mate for life. Evidence of lifetime mating has also been found in parrots, rooks, crows, eagles and a few small birds.

Swan courtship displays consist of performing a wing-flapping ritual dance in which the swans face each other and dip and turn their heads, ultimately touching heads as their necks intertwine to form a heart shape.

During the breeding season swans will aggressively defend their territory from other birds. Smaller birds, such as swifts and seabirds that breed in large colonies also demonstrate this behaviour.

Freshwater swans eat pondweed, stonewort and water grasses, as well as tadpoles and insects. They also seem to like fresh dandelions!

Saltwater swans typically eat sea grasses and algae, as well as insects and molluscs.

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blogit Highlights of some of your questions and answers. For the complete answers to these and lots of other questions visit: www.arkinthesky.org/en/blogit/blog

Richard, Oxford, UK comments: In your last issue you said that more than 100 million sharks are killed each year by

man – that’s not possible!

We asked ourselves the same question when we edited the article. One hundred million seems an improbable number of sharks to be killed each year. We double-checked our research and it is correct.

Having said this, we quoted the conservative estimate of the WWF and the Shark Research Institute. Greenpeace on the other hand reckons that around 270,000 sharks are killed globally every day due to the trade in shark fins. This is causing a serious decline in the world’s shark populations with many species under threat of extinction.

The UK shark protection organization Shark Trust reckons that around 73 million sharks are killed each year just for their fins, whereas the international shark protection initiative SharkProject speaks of around 200 million sharks being killed each year!

On this basis, we feel we were fairly accurate in our estimation of 100 million sharks being killed each year and the shocking thing is that they are killed mainly for their fins while the remainder of the mutilated shark is thrown back into the sea.

J. Jackson, Reading, Berks asks: When dinosaurs roamed the Earth there

were also prehistoric birds. How did birds survive when dinosaurs didn’t?

A recent study published in the Royal Society Open

Journal concluded that the shape of birds’ eggs could have helped them survive the mass extinction event that killed off the dinosaurs.

The team analysed the geometric properties of eggs from 250 million years ago (Mesozoic Era) to today. Before the extinction event that happened about 65 million years ago eggshells had notable differences to those that survived.

Modern-day birds descend from those that survived. The scientists pointed out, however, that this is just a small piece of the evolutionary puzzle of why one animal’s ancestors survived the extinction event and another’s didn’t.

Their analysis found that Mesozoic eggs were elongated and more symmetrical than all other bird eggs. Mesozoic bird eggshells were also more porous than expected for their size.

Dr Charles Deeming from Lincoln University noted that fossilized remains of eggs from 65 million years ago onwards (after the event that caused the dinosaurs to become extinct) were indistinguishable from modern bird eggs. The pre-extinction event eggs, however, differed significantly.

André, Paris, France asks: What do owls eat?

Like all birds, owls are carnivorous and therefore must kill other animals to survive. Their food depends largely on the size and species and includes insects, worms, spiders, snails, frogs and lizards.

They also eat other birds and small mammals such as mice and are known to prey on animals as large as themselves. Owls swallow their prey whole and what they cannot digest, such as bones and fur, is stored in their gizzard.

Strong muscles roll the undigested pieces into small balls called pellets, which the owl then regurgitates and discards.

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5 JANUARy – 13 FEBRUARy The Big Schools’ Birdwatch Free nationwide activity for UK schools and youth groups to assist in monitoring UK bird numbers as well as helping to get to know more about local birdlife.

2 FEBRUARy World Wetlands Day World Wetlands Day aims to raise public awareness of the values and benefits of wetlands.

7 – 15 FEBRUARy Big Farmland Bird Count Run by the Game & Wildlife Conservation Trust to raise awareness of the work being done by farmers for farmland birds. Farmers are being invited to record the bird species and numbers on their farms.

14 – 21 FEBRUARy National Nest Box Week Organized by the British Trust

MogliNoo, Cumnor, UK asks two questions: Why don’t ducks’

feet fall off in winter?

This is really interesting … The legs and feet of ducks are important in maintaining body temperature. Its webbed feet provide not only balance and mobility when swimming, walking, flying or diving, they also act as natural heating elements.

Ducks’ legs and feet have a special heat-exchange system known as “counter-current flow” where the arteries and veins in the duck’s legs are positioned closely to each other in order to maintain heat in the duck’s legs and wide, flat, webbed feet.

With its tea cosy-like feathery body-covering and naturally warm feet, very little of a duck’s body heat is lost through its extremities. So, while the body temperature of a duck standing on frozen ice would be nearly 38°C the temperature of its feet is maintained above freezing.

How do ducks breathe underwater?

Actually they can’t breathe under water – they have to hold their breath when they dive. This probably explains the reluctance of many newly-hatched ducklings to take that first plunge under water. They don’t take to it like a “duck to water” – it takes a few days even weeks for them to get the hang of it.

If you have ever watched ducks and swans disappear under water and come up again some considerable time later it does make you wonder how they can do it – but then again – as with all things – practice makes perfect and if you have been doing it virtually since birth and it is essential for your survival then you’re probably going to become pretty good at it.

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for Ornithology (BTO), the week encourages people to put up nest boxes in local areas to compensate for loss of natural nest sites. Various events take place around the country in support of the cause.

21 MARCH Intl. Day of ForestsInternational Day of Forests commemorates the contribution and value of forests and forestry to the community. It promotes awareness of the value of forests across the globe by providing information on forest protection, production and recreation.

3 MAy Intl. Dawn Chorus Day On International Dawn Chorus Day the public are encouraged to rise early to listen to birdsong at organized events.

9 MAy World Migratory Bird Day World Migratory Bird Day (WMBD) is a global a w a r e n e s s - r a i s i n g campaign highlighting the need for the protection of migratory birds and their habitats.

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When days get shorter and temperatures drop then birds lose body heat. Winter can be a very dangerous time for birds.

Birds have to eat several times a day in order to survive. By daybreak their energy

supply (which also works to keep them warm) is running out and they have to eat as soon as possible.

Cleverly, in order to compensate for loss in body temperature birds can also lower

their metabolic rate (the rate at which their bodies consume energy).

In Winter, birds have to eat enough every day to make it through a cold night. Just

two days of bitter cold and icy ground can kill many birds.

In cold-weather conditions, ready supplies of food are essential.

High-energy foods such as mixed seed, Nyjer seed, fat-balls, suet,

sunflower seeds and peanuts. Birds also enjoy grated cheese, cooked

rice and porridge oats!

Small seeds attract sparrows, finches, buntings and collared

doves. Tits and greenfinches like broken-up peanuts and sunflower

seeds. Flaked maize is preferred by blackbirds. Wheat and barley

grains are best suited to larger birds such as pigeons, doves and

pheasants – so putting these out in a small garden can frighten away

the smaller birds.

Fresh clean water is essential for seed-eating birds – not only to help them digest their food but also for

bathing and preening.

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Documents

majority of birds

extraordinary birds

largebrained birds

longdistance migrations

sky magazine

crane ark

great tits

effect of urban activity