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Dorling Kindersley (DK), 2011. — 514 p. in color. — ISBN: 140536291X, 9781405362917The beauty and drama of the bird world brought to breathtaking life in a new edition. From hummingbirds weighing less than a coin to monkey-eating eagles, this is a unique celebration of birds, photographed and studied in their natural environments around the world. Explore the complete bird story: from their origins to up-to-date information on flight, anatomy, feeding, communication, breeding, habitat, migrations and life cycles. Spectacular features on the most impressive birds, plus a huge catalogue that profiles nearly fifteen hundred different species makes this a must-have for every bird enthusiast. This title is published with Birdlife International, the world's leading avian authority.
Ano:
2011
Editora:
Dorling Kindersley Limited
Idioma:
english
Páginas:
512 / 514
ISBN 10:
140536291X
Serias:
BirdLife International
Arquivo:
PDF, 170,48 MB
Descargar (pdf, 170,48 MB)

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of

I L L U S T R AT E D

E N C Y C LO P E D I A

O F

I L L U S T R AT E D

E N C Y C LO P E D I A

O F

SENIOR EDITOR

Peter Frances
MANAGING EDITOR

Sarah Larter
PRODUCTION CONTROLLERS

Melanie Dowland, Shane Higgins
REFERENCE PUBLISHER

Jonathan Metcalf

MANAGING ART EDITOR

Louise Dick
SENIOR MANAGING ART EDITOR

Phil Ormerod
JACKET DESIGNER

Duncan Turner
ART DIRECTOR

Bryn Walls

SCHERMULY DESIGN COMPANY
PROJECT EDITOR

Cathy Meeus
EDITORS

Gill Edden, Jo Godfrey Wood, Ben Hoare

ART DIRECTOR

Hugh Schermuly
DESIGNERS

Steve Woosnam-Savage, Lee Riches

DK DELHI
DTP COORDINATORS

DTP DESIGNER

Balwant Singh, Sunil Sharma

Govind Mittal

EDITORS

Saloni Talwar, Alicia Ingty, Aditi Ray,
Ankush Saikia, Rohan Sinha, Pankhoori
Sinha, Aakriti Singhal
EDITORIAL MANAGERS

Dipali Singh, Glenda Fernandes

DESIGNERS

Mini Dhawan, Romi Chakraborty,
Tannishtha Chakraborty
ART DIRECTOR

Shefali Upadhyay
HEAD OF PUBLISHING

Aparna Sharma
BIRDLIFE INTERNATIONAL
PROJECT CO-ORDINATOR

Adrian Long

SPECIES DISTRIBUTION MAPPING

Mark Balman, Gill Bunting, Ian Fisher,
Simon Mahood, Dan Omolo, Louisa
Richmond-Coggan, Andy Symes

CONTENTS

LONDON, NEW YORK, MELBOURNE,
MUNICH AND DELHI

ABOUT THIS BOOK

6

FOREWORD by dr marco lambertini,
birdlife international
9

INTRODUCTION
BIRD ANATOMY

24

SENSES

26

FEATHERS

28

WINGS

30

FLIGHT

32

GLIDING AND SOARING

34

LEGS AND FEET

36

BILLS

38

FEEDING ON ANIMALS

40

FEEDING ON PLANTS

42

COMMUNICATION

44

DEFENCE

46

BREEDING

48

COURTSHIP

50

NESTS AND EGGS

52

PARENTAL CARE

54

LIVING TOGETHER

56

MIGRATION

58

MIGRATION ROUTES

60

BIRDS UNDER THREAT

62

CONSERVATION

64

EXTINCT BIRDS

66

AUDUBON
PROJECT CO-ORDINATOR

Sandy Pinto

EDITORIAL CONSULTANT

Sally Conyne

HABITATS

INDEXER

Sue Butterworth
PICTURE RESEARCHERS

Neil Fletcher, Will Jones
ILLUSTRATOR

John Woodcock

First published as Bird in Great Britain in 2007
This edition published in 2011 by
Dorling Kindersley Limited
80 Strand, London WC2R 0RL
; A Penguin Company (UK)
2 4 6 8 10 9 7 5 3 1
001 – 180274 – March/2011
Copyright © 2007, 2009, 2011 Dorling Kindersley Limited
All rights reserved. No part of this publication may be reproduced, stored in
a retrieval system, or transmitted in any form or by any means, electronic,
mechanical, photocopying, recording, or otherwise, without prior written
permission of the copyright owner.
A CIP catalogue record for this book is available from the British Library
ISBN 978 1 4053 6291 7
Colour reproduction by Colourscan, Singapore
Printed and bound in Singapore by Star Standard Ltd

See our complete catalogue at
www.dk.com

BIRD GEOGRAPHY

70

BIRD HABITATS

72

GRASSLANDS

74

DESERTS

76

TROPICAL FOREST

78

TEMPERATE FOREST

80

CONIFEROUS FOREST

82

HEATH AND SCRUBLAND

84

MOUNTAINS

86

POLAR REGIONS

88

WETLANDS

90

COASTS

92

OCEANS AND SEAS

94

FARMLAND AND CITIES

96

BIRD SPECIES
CLASSIFICATION

100

TINAMOUS

102

OSTRICHES

103

RHEAS

104

CASSOWARIES AND EMUS

105

KIWIS

106

GAMEBIRDS

107

WATERFOWL

120

PENGUINS

136

DIVERS

143

ALBATROSSES AND PETRELS

144

GREBES

152

FLAMINGOS

154

STORKS AND HERONS

158

PELICANS AND RELATIVES

170

BIRDS OF PREY

180

CRANES AND RELATIVES

206

WADERS, GULLS, AND AUKS

218

SANDGROUSE

243

PIGEONS AND DOVES

246

PARROTS

252

CUCKOOS AND TURACOS

272

OWLS

278

NIGHTJARS AND FROGMOUTHS

288

SWIFTS AND HUMMINGBIRDS

292

MOUSEBIRDS

300

TROGONS

300

KINGFISHERS AND RELATIVES

304

WOODPECKERS AND TOUCANS

315

PASSERINES

330

GLOSSARY

490

INDEX

494

ACKNOWLEDGMENTS

510

6

ABOUT THIS BOOK

CONTRIBUTORS
David Burnie Introduction, Habitats, introductions to bird orders

THIS BOOK IS DIVIDED INTO THREE CHAPTERS.

An overview
of the physiology and behaviour of birds is given in the
INTRODUCTION; the chapter on HABITATS looks at the distribution
of birds throughout the world, both in terms of geography and
types of habitat; and BIRD SPECIES, provides detailed information
on orders, families, and individual species of bird.

Ben Hoare Great Sites, introductions to passerine families, Glossary
Joseph DiCostanzo Introductions to passerine families
BirdLife International provided the text and maps for
the species profiles in this book. The species texts were written by the
following contributors:
Phil Benstead Gamebirds, Waterfowl, Pelicans, Waders, Gulls, and
Auks, Cuckoos and Turacos, Passerines
Chris Harbard Penguins, Birds of Prey, Kingfishers, Passerines
Guy Kirwan Rheas, Cassowaries and Emus, Penguins, Divers,
Albatrosses and Petrels, Pelicans, Cranes, Pigeons and Doves, Parrots,
Swifts and Hummingbirds, Mousebirds, Trogons, Kingfishers,
Woodpeckers and Toucans, Passerines (species and families)

INTRODUCTION
This opening chapter provides information on the physical characteristics of birds,
focusing on the aspects of their physiology that differentiate birds from the rest
of the animal kingdom. Bird behaviour is also examined, from different feeding
preferences and methods to systems of communication, courtship rituals, and
breeding and parenting. There is also coverage of migration behaviour and routes.
Threats to birds and steps being undertaken to protect them through conservation
efforts are also discussed in the closing pages of this chapter.
24

introduction

DIGESTIVE SYSTEM

BIRD ANATOMY
lungs
oesophagus

SOME GROUPS OF ANIMALS are easily confused, but there are no such
problems with birds. They are the only animals that have feathers, and
the only living vertebrates – apart from bats – that have evolved wings
and powered flight. Internally, they have a range of special features,
including hollow bones, powerful flight muscles, and a breathing
system that extracts the maximum amount of oxygen from air. Thanks
to these adaptations, some birds soar as high as passenger planes, while
others spend years on the wing before finally landing to breed.

kidney

All birds have evolved from the same distant ancestors
and, as a result, they share the same underlying
body plan. Their skeletons contain fewer bones
than a mammal’s, and they have bills
rather than teeth and jaws. Their wing
bones are light and hollow, and end in
a three-fingered “hand”, while their legs
have a Z-like shape, with a raised ankle
joint that looks like a backward-pointing
knee. In most birds, the ribcage is compact, but the breastbone has
a large vertical flap, called a keel, which acts as an anchor point for the
muscles that power the wings. In fast or powerful fliers, such as pigeons
and doves, flight muscles can make up 40 per cent of the body’s total
weight. These muscles generate a large amount of heat, helping birds
to maintain their high body
temperature, which averages
brachioradialis
straightens
40–42ºC (104–107ºF).

crop

glandular
stomach

heart

gizzard

liver
small
intestines
cloaca
pancreas

INTERNAL ORGANS
skull

upper
mandible

SKELETON AND MUSCLES

Birds have similar body systems to
mammals, but their organs differ. Most
have a crop and a gizzard in the digestive
system, and a single opening called the
cloaca for excretion and reproduction.

SKELETON

Birds often have long and highly
flexible necks, but the rest of the
backbone is much more rigid. The
keel projects forwards from the
breastbone. Immediately above it,
the furcula, or wishbone – formed
by a fusion of the collar bones –
functions like a spring when the
wings beat up and down.

lower
mandible

femur
air spaces

strengthening
struts

LUNGS AND BREATHING

Some birds – such as crows and gulls – eat
anything edible that they find, but most have
specialized diets and digestive systems that
have evolved to deal with particular foods.
Because birds do not have teeth, the majority
swallow their food whole. As it goes through
the digestive system, food is stored in the
crop before passing through a twochambered stomach. The first chamber, the
glandular stomach, secretes acidic digestive
juices. The second chamber, the gizzard, has
muscular walls which contract to grind up
food. After this, nutrients are absorbed and
waste expelled. Digestive systems are
modified in different ways. Seed-eaters have
large crops, so that they can eat rapidly and
DOWN IN ONE
move on. Many seabirds also have large
Birds often have a surprisingly
crops, to allow them to carry food back to
large swallow. This Doubletheir young. The Hoatzin’s crop is enormous,
crested Cormorant is tackling a
large fish – several minutes’ work. and functions like a microbial fermentation
tank, breaking down large quantities of
leaves. Glandular stomachs are largest in birds of prey, vultures, and fisheaters. The big Lammergeier Vulture produces such powerful stomach
acids that it can digest bones thicker than a human wrist. The gizzard is
largest in birds that eat seeds and nuts: many of these swallow grit and
stones that become lodged in their gizzards, helping to grind the food.
ilium

ischium

"2%!4().' #9#,%
trachea

interclavicular
air sac

biceps folds
wing against
body

triceps extends
wing away
from body
during flight

MUSCLE BOUND

posterior
thoracic air
sacs

INHALATION 1

At the start of the cycle, the forward and rear
air sacs expand. Inhaled air travels through the
bird’s trachea and into the rear air sacs.

LUNGS AND AIR SACS

A bird’s lungs take up less space than those
of a mammal, but they are much more
efficient. Air sacs act as reservoirs. Unlike
the lungs, they do not absorb oxygen.

anterior air sacs
compressing

Nick Langley Kiwis, Gamebirds, Storks and Herons, Birds of Prey,
Cranes and Relatives, Waders, Gulls, and Auks, Owls, Nightjars
and Frogmouths, Passerines (species and families)
Ed Parnell Storks and Herons, Birds of Prey, Cranes, Waders, Gulls,
and Auks, Parrots, Owls, Woodpeckers and Toucans, passerine families

 ANATOMY AND PHYSIOLOGY

Ian Peters Gamebirds, Birds of Prey, Waders, Gulls, and Auks, Parrots,
Cuckoos and Turacos, Swifts and Hummingbirds, Kingfishers,
Woodpeckers and Toucans, Passerines

posterior
air sacs
compressing

Craig Robson Waterfowl, Birds of Prey, Waders, Gulls, and Auks,
Sandgrouse, Pigeons and Doves, Passerines
Andy Symes and Richard Thomas Additional editorial support.

spongy bone

REPRODUCTIVE
SYSTEM

AIR-FILLED BONES

To save weight, many of a bird’s bones are
pneumatized, or filled with air. These air spaces
develop early in life, and are extensions of air
sacs that connect with the lungs. In the upper
arm, the bone material itself is spongy with air
sacs and the structure of the humerus is hollow,
but criss-crossed with fine struts that prevent
collapse of the delicate limb.

furcula
(wishbone)

pubis

ribs

sternum
fibula

radius

iliotibialis braces
knee and lifts leg

pectoralis minor
makes wings
flap upwards

posterior
air sacs
anterior air sacs
expanding
expanding
lung

abdominal
air sacs

tail
vertebrae

neck
vertebrae

ulna

pectoralis major
makes wings flap
downwards

trachea

lung

pygostyle

flexor carpi ulnaris
folds wingtip

5NLIKE MAMMALS BIRDS TAKE TWO
COMPLETE BREATHING CYCLES TO
MOVE A SINGLE BREATH IN THROUGH
THE TRACHEA THROUGH THE LUNGS
AND BACK OUT OF THE BODY 7HEN
·YING THEIR BREATHING RATE CAN
SPEED UP BY  TIMES TO POWER
THE EXTRA ENERGY REQUIRED

cervical
air sacs

anterior
thoracic
air sacs

James Lowen Tinamous, Ostriches, Waterfowl, Gamebirds, Flamingos,
Owls, Kingfishers, Woodpeckers and Toucans, Passerines

These pages include detailed
descriptions of the physical
characteristics of birds and the
ways in which these have
evolved to serve the needs
of different types of bird in
a variety of environments.

When a mammal breathes, air flows into its lungs and back out again.
Bird lungs work differently: air flows straight through the lungs, via a
system of air sacs, before being exhaled. This one-way flow allows air
and blood to move in opposite directions, known as countercurrent. As
a result, bird lungs are more efficient at transferring oxygen and carbon
dioxide than those of mammals, so that some birds can fly at over
10,000m (33,000ft) – an altitude where a mammal would lose
consciousness. Most flying birds have nine air sacs, which connect with
air spaces in major bones. Diving birds have poorly developed air spaces,
but in some land birds – such as hornbills – they reach as far as the toes.

wingtips

Most of a bird’s muscles
are packed close to its
body, giving it a
streamlined shape. In
flying birds, the largest
muscle is the pectoralis
major – this produces
most of the power needed
for flapping flight.

25

bird anatomy

Krys Kazmierczak Grebes, Storks and Herons, Cranes, Waders, Gulls,
and Auks, Passerines

external
digits
(fused
together)

flexors
bend toes

All birds reproduce by laying eggs. Apart from
mound-builders, or megapodes, all of them
incubate their eggs by sitting on them, and play some part in caring for
their young. In many birds, the reproductive system follows an annual
rhythm, switching on at the beginning of the breeding season, and then
shrinking again when its work is done. Female birds usually have a single
ovary, which produces eggs like units on a production line.
Eggs contain all the nutrients that a developing embryo
needs, but they do not start to develop until the eggs
are laid, and incubation begins.

EXHALATION 1

Both sets of air sacs are now compressed, so
that air is squeezed out of the rear air sacs
and into the lungs.
anterior air sacs
expanding

posterior
air sacs
expanding

MATING BEE-EATERS

NERVOUS SYSTEM
“thumb”

spinal cord

BRAIN AND
SPINAL CORD

A large part of a bird’s
forebrain is devoted to
vision. The large
cerebellum deals with
movement and balance.

To fly, birds need fast reactions, and an ability
to process rapidly changing information,
particularly from their eyes. Their brains are
well developed and, in small birds, they can
be twice as big as in mammals of a similar size.
As well as flying, birds carry out many kinds of
complex behaviour, from courtship rituals to longdistance navigation. Most of this behaviour is “hardwired” into their nervous systems, which means that it does
not have to be learned. However, birds do learn new forms
of behaviour as they grow up, and some of their instinctive
skills – such as nest building – improve with experience.

metacarpus
tarsometatarsus

INHALATION 2

The air sacs expand again, drawing more air in
through the trachea. Meanwhile, air already in
the lungs moves into the forward air sacs.
anterior air sacs
compressing

posterior
air sacs
compressing

metatarsus

THE SKULL

tarsus

digit

Bird skulls are strong, although often
paper-thin. Seen from above, this scan
of a bird skull shows the circle of bony
plates, called the sclerotic ring, which
supports each eye.

EXHALATION 2

32

To finish the double cycle, the air sacs are
compressed, driving the air in the forward air
sacs back out through the trachea.

introduction

INTRODUCTION

INTRODUCTION

In birds, as in mammals,
eggs are fertilized inside
the female’s body. In some
species, the female can
store the male’s sperm for
several weeks.

cerebral
hemispheres

FLIGHT

BIRD FLIGHT 

NESTS AND EGGS
rarely make homes for themselves.
Instead, most of their nests are used solely for raising young. Some birds
lay their eggs directly on the ground or in a tree hollow, but many make
elaborate structures from an immense range of building materials,
including twigs, leaves, mud, spiders’ webs, saliva, and even
rotting seaweed. A nest helps to conceal vulnerable
hatchlings, and it also insulates them – a crucial
feature if they have no insulation of their own.

FLIGHT PATTERNS

LANDING

To land, a songbird drops its airspeed
until it is just about to stall. With its
wings and tail both acting as brakes,
it drops onto its perch. Small birds
such as this European Robin weigh
little, so come to a standstill quickly.

PERMANENT NESTS

#/--5.!, .%343
-ANY BIRDS NEST IN GROUPS BUT
A FEW SPECIES BUILD NESTS THAT ARE
PHYSICALLY ATTACHED TO EACH OTHER
4HE RESULT IS A GIANT COMMUNAL
NEST LIKE A BUILDING WITH LOTS
OF SELF CONTAINED APARTMENTS
)N !FRICA 3OCIABLE 7EAVERS
MAKE COMMUNAL NESTS OUT OF
GRASS IN 3OUTH !MERICA -ONK
0ARAKEETS USE STICKS

SHARED ACCOMMODATION

The communal nests of Sociable Weavers are
usually built in isolated trees. They can contain
up to 300 separate nesting chambers, each
with its own downward-pointing entrance.

RHINOCEROS HORNBILL

HARPY EAGLE

Fragmented habitat threatens
large birds of prey throughout
Central America.

RED-HEADED PICATHARTES

Forest fragmentation in Africa
now endangers both species
in this small family.

78

habitats

tropical forest

in tropical
forest than any other habitat, despite the
ravages of deforestation. Some species are
well known for their vivid colours, but
there are many less conspicuous
birds that also live in this
habitat. The bird life is strongly
influenced by climate, and there are
major differences between the birds of
the Old and New World tropics.

MORE BIRD SPECIES OCCUR

egg white
(albumen)

Central and South America remain
unequalled in the richness of their birds.
Many bird families are restricted to the
Americas, and for the overwhelming
majority, rainforests are by far the most
important habitat. These families range from
toucans and cotingas – some of the most
flamboyant and vocal of all forest birds –
to antbirds and tapaculos, whose drab colours form
highly effective camouflage. Other American
rainforest species include tyrant flycatchers,
hummingbirds, and American blackbirds and orioles.
Fruit-eating birds, such as toucans and quetzals,
play a key role in tropical forests because they help to
spread seeds. Many other forest birds actually feed on
seeds and nuts. In the Americas, the most conspicuous
among them are macaws – the world’s largest parrots
– which are found only in this region. Generally
speaking, tropical forests are difficult habitats for
scavengers and birds of prey, since the dense cover
makes it hard to find food. However, the American
tropics are home to several spectacular examples,
including the King Vulture and Harpy Eagle.

SHAPE AND COLOUR

Some eggs are almost
round; guillemot eggs
have a sharp point, to
stop them rolling off
cliffs. The shell has
a basic colour, with
markings added
just before laying.

REDSHANK

yolk

air
cavity

developing
embryo

INSIDE AN EGG

An egg is lined with a series
of membranes that help to keep
water in, but which let oxygen
and carbon dioxide pass
through the shell. As the
embryo grows, the yolk (which
provides nourishment) shrinks,
and the air space enlarges.
The shell thins, as its calcium is
used for the embryo’s skeleton.

GUILLEMOT

OSPREY

AMERICAN
ROBIN

MAGNIFICENT
RIFLEBIRD

INTENSIVE AGRICULTURE
With over 6 billion people to support now, and over 9 billion expected
by the middle of this century, food production has never been more
important. Increasingly, food is supplied by intensive farming – a form
of agriculture that depends on the routine use of artificial fertilizers and
pesticides. Intensive farming produces high yields, but this comes at
a high price to the environment. With wild plants and insects kept at
very low levels, birds soon run short of food. As a result, species that
were once a common sight in rural areas are in rapid decline. In Europe,
intensive agriculture has had a particularly damaging effect on groundnesting species such as the Eurasian Skylark and Northern Lapwing,
and similar declines have affected farmland birds in many other regions.

birds under threat

ON DANGEROUS GROUND

In intensively farmed areas, larks
such as this Eurasian Skylark face
a double threat to survival. Food is
hard to find, and as ground-nesters,
they also risk having their eggs or
nestlings destroyed by tractors.

Over the centuries, humans have accidentally or deliberately introduced
alien species to far-flung parts of the world. For birds, this mixing up of
the world’s biodiversity has had extraordinarily damaging results. Since
1500, about 150 species of bird have become extinct, and in half these
cases, introduced species have been the chief cause. In some cases, these
undesirable aliens are predators that have a direct and deadly effect on
local birds. Cats and rats are often the culprits, particularly when they
arrive on remote islands that have no native mammals of their own.
Both are highly efficient predators, not only of adult birds, but also of
nestlings. More subtle, but no less dangerous, is the effect of introduced
grazing and browsing animals, such as goats. These can strip islands of
their native vegetation, which removes the cover that many birds need
to breed. Finally, introduced species may bring disease. In the Hawaiian
Islands, for example, introduced mosquitoes brought with them avian
malaria and avian pox. At low altitudes, where mosquitoes are abundant,
many of the islands’ native birds have disappeared.

VULNERABLE GOOSE

LONG-BILLED
SPIDERHUNTER

Spiderhunters are
named for their habit
of plucking spiders
from their webs, but
also (as here) feed on
nectar. They belong
to the sunbird family,
and like other sunbirds
build hanging, pouchshaped nests.

MONSOON FOREST

GREEN IMPERIAL PIGEON

This Asian forest pigeon feeds mainly
on soft fruit, digesting the flesh but
scattering the seeds in its droppings.
GREAT BLUE TURACO

Also known as the
Blue Plantain-eater,
this large forest bird
occurs throughout
much of equatorial
Africa. Pairs or small
family groups can be
seen feeding on fruit,
flowers, and leaves in
the tops of tall trees.

KEEL-BILLED TOUCAN

Fruit and a variety of small animals
feature on the Keel-billed Toucan’s
menu. The species is widespread
in America’s lowland rainforests.

UNCERTAIN CATCH

Albatrosses and gannets
swoop around a trawler off
the coast of South Africa. The
huge growth in fish catches
has had damaging effects
on birds’ food supply.

Pesticides and other
organic pollutants are a
major threat to the world’s
birds. In southern Asia,
vultures have declined by
up to 95 per cent in less
than a decade – a sideeffect of the veterinary
drug Diclofenac finding
its way into dead remains.

CLIMATE CHANGE

Like many migrants, the
Red-breasted Goose has a
sharply defined distribution,
which has evolved over many
thousands of years. Its main
breeding area lies in the
remote Taymyr Peninsula in
northern Siberia, a region
that is currently experiencing
rapid climate change.

ARCTIC OCEAN

TOTAL DESTRUCTION

This is the largest
vulture found in
American tropical
forests – and by far
the most colourful.
It locates food by
smell and its diet
includes dead
mammals in the forest
itself, as well as dead
fish washed up on
riverbanks.

This enormous eagle hunts up in the
forest canopy, where it is a predator of
monkeys and colugos (flying lemurs).

Thanks to their long geological links (see Bird
Geography. p. 70), Africa and Asia’s tropical forests
share many families of birds. Among the most
impressive are the hornbills, which are the Old World
counterpart of toucans. Hornbills live in a variety
of habitats, but the largest species are found in the
forests of southeast Asia. Old World tropical forests
are also an important habitat for bulbuls – mediumsized songbirds that often have crests. Dozens of
species live in tropical forests, and although many
are secretive, some visit gardens near forested land.
Flower-visitors include sunbirds, which probe deep
into blooms with their long curved bills, and whiteeyes. Compared to most nectar-feeders, white-eyes
have short bills, and they often reach their
food by pecking holes in the base of flowers.
In temperate regions, pigeons are typically
drab-looking birds that feed in the open. But
in the Old World tropics, dozens of species
of sumptuously coloured pigeons and fruitdoves live and feed in forests. Some species
are widespread, while others are localized,
particularly in the islands of southeast Asia
and the western Pacific. Despite their brilliant
colours, fruit-doves can be difficult to see.
Parrots are different: their bright plumage and
noisy habits often make them a conspicuous
part of the forest fauna. Some of the most
colourful kinds, such as lorikeets, feed mainly
at flowers, lapping up pollen and nectar with their
brush-tipped tongues. Australasian tropical forests
are home to two highly distinctive families found
nowhere else: the cassowaries and birds of paradise.

Unlike tropical rainforest, monsoon forest has
a sharply defined wet season, followed by months
of drought. Many monsoon forest trees are deciduous,
losing their leaves during the dry season, and they
sometimes flower while their branches are still bare.
The largest area of this habitat is found in southern
Asia. Here, forest birds include hornbills, parrots, and
many species of babbler. There are also a wide variety
of gamebirds, including the Indian Peafowl and the
Red Junglefowl – the wild ancestor of the farmyard
chicken. Like most gamebirds, they feed on the
ground but roost in trees.
MALABAR PIED HORNBILL

Resident in southern Asia from
India to Sri Lanka and Borneo,
this hornbill prefers open forest,
often near human habitation.

ORGANIC POLLUTANTS

INTRODUCED SPECIES

Modern combine harvesters are highly
efficient, and leave little or no waste
grain for birds to glean. Intensive farming
also compacts the soil, reducing the
supply of earthworms and small animals.

On a hillside facing the Mediterranean, two Maltese
hunters pick off migrating birds. Often defended on the
grounds of tradition, this destructive “sport” has been
attacked by conservation organizations, leading to a
tightening of regulations in recent years.

Throughout the world, birds are exploited for food,
for sport, and for the cage-bird trade. Hunting can be
particularly damaging, because the targets are often birds
on migration, which are easy to pick off where they
cross mountains or coasts. Even in countries where the
hunting season is controlled, regulations designed to
protect migrants are often ignored. The cage-bird trade
affects some bird families far more than others. For example, over 50
species of parrot – out of a total of 352 – are in serious danger. Some
other commercial activities, particularly fishing, also have damaging
effects. Some birds, such as gulls, thrive on fishing waste, but the picture
is very different for diving birds, such as guillemots and puffins, which
face increased competition for food. Albatrosses are in a steep decline,
following the growth of long-line fishing. Every year, many thousands
of albatrosses drown after taking long-line baits and becoming hooked.

HABITAT LOSS

CLEAN SWEEP

63

HUNTING FOR SPORT

EXPLOITING BIRDS

PHILIPPINE EAGLE
SCARLET MACAW

Like many other forest
parrots, the Scarlet
Macaw flies over the canopy in noisy
flocks to and from its night-time roosts.
It is one of the most abundant macaws.
KING VULTURE

AMERICAN
RAINFOREST

79

AFRICA AND ASIA

TROPICAL
FOREST

MALE IN CHARGE

Ostriches lay their eggs directly on the ground. Several females
contribute to the clutch, which is guarded by a single male.
Eventually, the nest may contain over 50 eggs. Only half of
them are incubated – the ones at the edge do not hatch.

The destruction of natural habitats is the
biggest threat that birds face today. Farming
and forestry are the main driving forces,
followed by the growth of cities, and
development of coasts. Most birds are adapted
to a particular habitat and cannot survive
elsewhere. As a result, widespread birds
become more localized, while those that were
localized to begin with risk becoming extinct.
Habitat destruction is not new – it dates
back to the start of farming, about 10,000
years ago. However, it has never taken place
on the scale seen today. Deforestation in the
tropics hits the centre of bird diversity,
while the growth in cities and
infrastructure takes its toll on bird
life all around the world. When
cities spring up on what used to be
forest or wetlands, the environmental
damage is clear to see. But habitat
destruction also occurs in less visible
ways. For example, oil palms or fastgrowing conifers are often grown on
land where the natural forest cover has
been cleared. These plantations may
look green and lush, but their bird life
is only a faint echo of the richness in
natural forest habitats.

Deforestation affects birds worldwide.
Charred stumps are all that remain of
these eucalypt trees cut for timber in the
Central Highlands of Victoria, Australia.

Only hummingbirds, kingfishers, and kestrels
routinely hover for extended periods. Feeding
at a flower, this Mangrove Hummingbird may
beat its wings 50 times a second.

In the coming decades, climate change threatens to become the biggest
challenge facing the world’s birds. As climate patterns change, natural
habitats are likely to shrink or shift, making it harder for birds to find
food and to breed. The outcome of this is hard to predict – all that
can be said with any certainty is that birds with highly specific
ecological needs are likely to be the hardest hit. These needs can
take many forms. For example, the Red-breasted Goose breeds in
tundra in one part of northern Siberia, and relies on this habitat for
its survival. If the region continues to warm at its present rate, this
goose’s breeding habitat will shrink dramatically, making its population
plummet. Many other species will be affected by changes in vegetation,
or by shortages of food at the time when they normally breed. At sea,
gradual warming is likely to disrupt
normal patterns of plankton growth.
As a result, fish supplies will become
less reliable, creating food shortages for
seabirds. The outcome, for birds, is a
world where there are some winners,
but far more losers. In the long run,
a substantial proportion of these risk
becoming extinct.

Russia

Arctic

Circle

Key
Red-breasted Goose breeding area

tundra loss

no change to tundra extent

tundra expansion

A SHRINKING HABITAT

This map shows projected changes in the tundra
of northern Siberia, assuming that the current
warming trend continues. By the year 2070, up
to three-quarters of the area of the Red-breasted
Goose’s nesting grounds are likely to be invaded
by trees, thereby preventing it from breeding.

tropical forest

FORK-TAILED WOODNYMPH
TROPICAL FOREST DISTRIBUTION

Rainforest is found worldwide on and near the equator, where intense
sunshine produces almost daily downpours of rain. Towards the edges
of the tropics, the climate is much more seasonal. Here, evergreen
forest gives way to monsoon forest, which is dry for much of the year.

In the Americas, hummingbirds are
important pollinators of forest flowers.
Despite their small size, the males can
be pugnacious, attacking each other in
mid-air to defend patches of flowers.

a map indicates
the main areas
of the world in
which the habitat
exists

OLIVE SUNBIRD

The Olive Sunbird from tropical Africa is
a highly active species that flits between
forest flowers like a hummingbird.

HABITATS 

Pages such as the ones shown here
describe different habitats and a
selection of the typical bird species
that are found in that habitat.

HABITATS

Hornbills are threatened by a
wave of deforestation that is
sweeping southeast Asia.

RANDOM FLAPPING

This flight pattern is typical of aerial insecteaters, such as swifts and swallows, and
also of some larger birds, including kites.

HOME SECURITY

BIRDS UNDER THREAT

BIRD CONSERVATION 

SLOW FLAPPING

A wide variety of birds, including harriers,
gulls, and Barn Owls, flap their wings slowly
so that they can scan the ground for food.

INTERMITTENT FLAPPING

This flight style produces an undulating path,
and the longer the intervals between flapping,
the more noticeable the undulations.

This chapter opens with an overview of the
biogeographical realms in which birds are distributed
throughout the world, and the ways in which different
groups of birds have evolved in different regions over
millions of years. An overview of the variety of
environments - or biomes - in which bird life exists
is followed by a detailed description of each main type
of habitat, from polar regions to deserts and urban
environments. These accounts include information about
the bird species that are adapted to these conditions and
their lifestyle, including diet, nesting, and migration.

Standing by its nest, this Gentoo Penguin is
not only guarding its egg, but also its nesting
materials. Neighbours are quick to help
themselves if materials are in short supply.

double
membrane

A bird’s egg is a single giant cell, protected
by watertight membranes and a porous shell.
The embryo starts to take shape during
incubation, when the original cell divides
repeatedly, creating the tissues and organs
of a developing bird. Seabirds often produce
a single egg, while gamebirds lay the largest
clutches: some species, such as quails and
partridges, can produce over 20 eggs each
time they breed. There is no straightforward
connection between a bird’s size and the size
of its eggs. The Bee Hummingbird produces the
smallest eggs – as little as 7mm (1/4 in) long –
while the Ostrich’s are the largest, weighing up
to 1.5kg (31/3 lb). However, the Kiwi’s solitary
egg is the biggest in relative terms, measuring
62
introduction
about a quarter
of the female’s weight. The eggs
of cavity nesters are often white, while those
of ground-nesters are usually camouflaged.

HABITATS

Covering topics such as social
behaviour, courtship, nesting,
breeding, and migration, this
section addresses all aspects
of how birds behave.

GROUND NESTERS

EGGS

FAST FLAPPING

Pigeons and ducks both have a fast, direct
flight – a characteristic shared by auks and
cormorants as they speed over the sea.

 BIRD BEHAVIOUR

ANCESTRAL PILE

A large number of birds – particularly in open
habitats – lay their eggs on the ground. Many use
no nesting material, relying instead on camouflage
or out-of-the-way nest sites to protect their eggs and
young. These birds include many seabirds and waders,
as well as nightjars, some vultures, and large flightless
birds, such as ostriches and emus. Some excavate a
shallow depression called a scrape, but guillemots and
razorbills do not have this option. They breed on cliff
ledges, and lay a single egg directly on the bare rock.
In addition to these “non-builders”, groundnesting birds include many species that have at least
some construction skills. Penguins often breed on
rocky shores, gathering small piles of stones or sticks.
Waterfowl and gamebirds show greater expertise,
building bowl-shaped nests from plants. The largest
structures are built by megapodes: their moundshaped nests can be over 10m (33ft) across and up
to 5m (17ft) high, containing several tonnes of leaves.

feet are stowed
away close to
body

HOVERING

53

nests and eggs

splayed tail
feathers help
to generate lift

A Bald Eagle looks out from its nest high in a pine tree. Bald Eagles
make the world’s biggest nests – the largest one ever measured was
nearly 3m (10ft) wide and over 6m (191/2ft) deep. These giant nests are
often built by several generations of birds.

INTRODUCTION

INTRODUCTION

wings almost
meet at top of
upstroke

Birds often have characteristic flight patterns,
which can help to identify them when they are
on the wing. Some follow a level flight path, flapping their
wings at a steady rate, varying from about 200 beats a minute
for pigeons, to a much more leisurely 25 beats a minute for
large birds such as herons. Many other birds intersperse flapping
with short bursts of gliding, but some species dip up and down,
flapping their wings in short bursts, and then holding them
against their sides. This is common in finches, which have
an undulating or “bouncy” flight path, and it is even more
pronounced in woodpeckers and toucans.

RECENT ESTIMATES PLACE 12 per cent of the world’s birds
– over 1,200 species – at threat of extinction. This is
catastrophic, and not only for birds themselves, because
their changing fortunes mirror the
health of the global environment.
Birds are threatened in many ways,
but most current problems have the
same root cause: human-induced
changes to the natural world.

The final part of this
chapter examines how
birds are adapting to
conditions in the modern
world. As well as looking
at the threats, it also
describes the positive
steps that being taken to
conserve bird species.

alula is raised
during take-off

wings point
forwards while
rising from
downstroke

INTRODUCTION

Tree-holes and other natural cavities
are used as nests by a wide range of birds. At one
extreme, these include small songbirds such as tits;
at the other are 1m- (3ft-) long hornbills, and macaws.
Woodpeckers excavate holes themselves, but many other birds take
them over once the original owners have moved on. Hornbills have
a particularly unusual form of cavity nesting behaviour. Having
found a suitable nest hole, the female moves in. The male then
seals the entrance with a wall of mud, leaving a small hole
so he can supply his mate with food. Cavity nesters also
include birds that burrow into the ground, or into riverbanks, or sandy
cliffs. Most use their beaks to peck their way through the earth, although
the North American Burrowing
STARTING FROM SCRATCH
Owl excavates with its feet. BankWoodpeckers can chisel holes in healthy, living
nesters, such as kingfishers, often
wood. Once the hole has been opened up, the
give their tunnels a slight upward
wood eventually begins to rot, allowing other
slope to prevent them from
birds to expand the nest in subsequent years.
A Eurasian Three-toed Woodpecker is pictured.
becoming flooded.

At dusk a male Eurasian Woodcock carries
out its courtship flight. This is the slowest
bird flight not to involve gliding or hovering.

Seen in cross-section, a bird’s wing forms a shape called an aerofoil.
Air moves over the upper surface faster than the lower one, causing
a reduction in pressure that results in lift. If lift is greater than the pull
of gravity, the bird rises, and if thrust exceeds drag, it accelerates
forwards. But if each pair of forces is balanced, the bird stays
at the same height and speed.

Songbirds usually abandon their nests when their young
have fledged, and build new ones next time they breed.
This sounds wasteful, but it is a good way of avoiding
the attention of predators and reducing parasite
infestation. Birds of prey are different: they frequently
return to the same nest year after year. With each
breeding season, they add more sticks, increasing the
size of the nesting platform. Because these birds are
long-lived, the largest species – such as Bald Eagles –
can end up owning nests of a colossal size. White
Storks also reuse their nests, but the most remarkable
permanent nests are made by the African Hamerkop.
Although only about 30cm (12in) high, this marshland
bird builds an immense spherical nest out of sticks, up
to 2m (61/2 ft) across. The Hamerkop’s nest
is multi-chambered, and is so strong that
it can support the weight of an adult man.

Safely beyond the reach of most predators,
these Cliff Swallow nests are made of
mud mixed with saliva – a material
that becomes rock-hard as it
dries, and lasts for years.

CAVITY
NESTERS

LEISURELY FLIGHT

Birds have a strict “baggage allowance” that
limits their own body weight, and also the
weight of anything they carry into the air. The
strongest lifters are birds of prey, which carry
their victims in their claws. The large, fully
grown trout that this Osprey is carrying may
equal half its body weight.

WING AERODYNAMICS

LIFTING OFF

When birds take off, their wings work
in complex ways. Instead of pushing
downwards and backwards like a pair
of oars, a pigeon’s wings twist at the
bottom of the downstroke, helping to
pull the bird through the air like a pair
of propellers. To reduce turbulence, the
primary flight feathers are spread apart
and the alula, a small feathered flap
that protrudes from the “wrist” of each
wing, is temporarily raised.

BUILDING WITH MUD

Songbirds are usually blind and featherless when they
hatch, so a robust nest is essential for their survival.
The majority of species nest off the ground, chiefly
in trees and bushes, but songbirds also nest on rocks,
in caves, and even behind waterfalls. Their nests are
typically cup-shaped, but evolution has produced all
kinds of refinements to this basic design. One of the
commonest is the domed nest with an entrance at
one side. Even more effective, in security terms, are
nests that hang from the ends of slender branches.
Weavers often build nests like these, but the largest are
made by oropendolas in tall tropical trees. Shaped like
an extended pouch, their nests can be up to 2m
(61/2 ft) long, with the living quarters hanging up to
50m (160ft) above the ground. However, songbirds
are not the only tree-nesters: this behaviour is
widespread in many other birds. Ovenbirds, which
also belong to the passerine order – build some of the
most complex nests of all. Shaped like an old-fashioned
clay oven, the nests have a slit-like entrance and a curving
corridor leading to the nest chamber
inside. Non-passerines typically make WEAVER AT WORK
Nest-building is controlled by instinct, but
crude platform nests from sticks.
Even elaborate nests are built quickly. requires enormous skill. Using strips of grass, male
Southern Masked Weavers build ball-shaped nests
A structure that requires thousands
that hang from the tips of branches. Once the nest
of billfuls of moss or leaves can be
is complete, the male hangs upside down beneath
it, and flutters his wings to attract passing females.
complete in a couple of days.

widely spread
flight feathers
increase wing’s
surface area

AIRLIFT

gravity

TAKEOFF AND LANDING

UNLIKE MAMMALS, ADULT BIRDS

NESTING OFF THE
GROUND

airflow

drag
bird’s wing
thrust

Body weight has a far-reaching effect on the way birds take off
and land. Small songbirds can take off in a split-second with just
a kick of their legs, but heavily built birds take much longer to
get into the air. Pheasants and other gamebirds are a notable
exception to this rule: powerful flight muscles give them an
explosive take-off to escape from danger. Taking off can be
hard work, and in heavy birds, the wing’s geometry changes
to maximize lift and minimize energy-wasting turbulence.
These changes are reversed once the bird is in the air.
Landing requires careful coordination, and also plenty
of space in the case of heavy birds such as bustards and
swans. When birds land, they increase the angle of
their wings, like an aeroplane lowering its flaps.
The bird then swings its legs forwards, and if all
goes to plan, it lands on them without toppling
over. But for a heavy bird, such as a swan,
it is very difficult to lose so much
momentum in a short time. Instead,
swans land on water, using their
large webbed feet as brakes.

INTRODUCTION

introduction

With its wings partly folded,
a Peregrine Falcon dives,
or stoops, towards its
airborne prey hundreds
of metres below.

INTRODUCTION

52

POWER DIVE

lift

FLIGHT FORCES
Flapping flight is a highly complex form of
movement, which is still not fully understood.
However, the basic principles behind bird flight are
well known. Like aircraft, birds have to generate two
forces to fly. The first, known as lift, counteracts the
downward pull of Earth’s gravity. The second force,
called thrust, counteracts air resistance or drag, and
pushes the bird forwards. In both birds and aircraft,
lift is produced by the stream of air moving over the
curved surfaces of the wings, while in most birds
thrust is produced by flapping. However, bird wings
are highly flexible, and so flapping flight can involve
many other factors as well. For example, pigeons
generate extra lift by bringing their wings together
on the upstroke, while hummingbirds can generate
a constant downdraught by making each wing trace
a path like a figure 8. Gliding birds (see p.34) are quite
different: they exploit the air currents around them,
saving much of the energy required in flapping flight.

This key aspect of bird
behaviour is examined
in detail, including
aerodynamics, different
types and patterns of
flight of a variety of
bird species.

33

FLIGHT SPEEDS
The speed of a flying bird is difficult to measure, so many records from
the early years of ornithology are now thought to be unreliable. Birds are
also experts at taking advantage of prevailing winds, and wind-assisted
flight can make some long-distance speed records misleading. However,
there is little doubt that the Peregrine Falcon holds the absolute record
for speed in the air. When it is diving, it probably exceeds 200kph
(124mph). The fastest birds in level flight are ducks, geese, and swifts.
Some of these can reach an airspeed of nearly 80kph (50mph). In general,
birds rarely fly faster than 30kph (18mph).The slowest birds of
all – woodcocks – can fly at a leisurely 8kph (5mph) without
stalling, which is not much faster than a brisk walk.

huge advantages, particularly in the search
for food. Over millions of years, it has evolved independently in several different
groups of animals, including flying reptiles called pterosaurs, whose leathery wings
were up to 12m (40ft) across. Today, the animal kingdom includes many species that
can glide, but only three kinds of animal – birds, bats, and insects – can stay airborne
by flapping their wings. Of these, insects are by far the most numerous, but birds lead
the field in speed, endurance, load-carrying capacity, and total distance flown.
THE POWER OF FLIGHT GIVES ANIMALS

HABITATS

cerebellum

7

BIRD SPECIES
This final chapter is devoted to a detailed look at over
1,200 bird species. It opens with an overview of the
different ways in which birds are classified. The rest of
the chapter is organized according to taxonomic order,
with the non-passerine orders being covered first,
followed by the passerines. Introductory sections
describing the different bird orders and, in the
passerine section, bird families are followed by profiles
of individual species within that group. In most cases
each species profile includes a photograph of the bird,
a map showing where it is found, summary data
detailing its size, migration status, and preferred habitat.
For the most threatened species, information is also
given on status according to the IUCN Red List.
The chapter is interspersed with illustrated accounts
of great bird-watching sites around the world.

Resident. Areas inhabited
by non-migrant birds.

Partial migrant

24cm (91/2in)

A common bird in its large range of
southeast Asia to Australia, the Collared
Kingfisher is also known as the Whitecollared, Sordid, or Black-masked
Kingfisher.The plumage varies across
the 49 races of the species, with
differences in the blueness or greenness
of the upperparts, the extent of the pale
spot above the bill, and the whiteness of
the underparts.

22cm (81/2in)
WEIGHT

40g (17/16oz)
MIGRATION

Partial migrant
Woodland and thickets, especially along
watercourses, bushy grassland, and parkland
HABITAT

The Grey-headed Kingfisher is
primarily insectivorous, preying on
grasshoppers, crickets, and locusts in
particular. Most prey is taken from the
ground, but some insects are caught in
flight. Small prey are swallowed whole,
while larger insects may be smashed
against a perch. Pairs display by singing
from a treetop and flicking open their
vivid blue wings. They also circle high
above the ground, calling constantly,
before diving back to a tree.
The timing and extent of the
species’ migratory movements vary
across its African range. Only birds in
Cape Verde, the East African coast, and
perhaps in equatorial Africa are
resident, while those at mid-latitudes
and some southern areas undertake
a complex three-stage migration.

The Yellow-billed, Lowland, or Sawbilled Kingfisher is found in the forests
of New Guinea. This small kingfisher
often raises its crown feathers, creating
an alarmed appearance. It has a strong
orange-yellow bill, white throat, rufous
head and underparts, greenish blue
upperparts, and a dark blue tail.
The juvenile has a dark grey bill.
The species feeds primarily on
insects, but will also take worms, small
lizards, snakes, and reptile eggs. It perches
in the canopy, higher than many
kingfishers, swaying from
side to side as it searches for prey.
When it spots a movement,
it swoops and grabs its prey.
ADULT YELLOWBILLED KINGFISHER
Its call is a whistling trill.

16cm (61/2in)
WEIGHT

45–65g (15/8–23/8oz)
MIGRATION

ADULT RUDDY KINGFISHER

Partial migrant
Eucalyptus and open woodland, scrub,
forest edges, farmland, and coastal habitats
HABITAT

Halcyon coromanda

Ruddy Kingfisher
LENGTH

Partial migrant

The Sacred, Wood, Tree, or Green
Kingfisher has a prominent black
eye mask and a green back, wings,
and tail, with pale underparts. Its
diet includes insects, worms, small
fish, lizards, birds, and mice, which
it spots by perching on a vantage
point and scouring the area below
for movement.

BIRD SPECIES

WEIGHT

650–700g (23–25oz)
MIGRATION

Non-migrant

The Red-billed Tropicbird is the
largest member of a family of three
distinctive species. The plumage of all
three species is mainly white with

black markings on the head and
upperparts, but the Red-billed
Tropicbird is distinguished by its red
bill, black nape band, barred back, and
white tail streamers. It has
a long body, thick neck,
and long, narrow wings.
The tail is extraordinary, with
the central pair of tail feathers
elongated into elegant streamers that
trail behind in flight. The bill is
powerful, with a sharp, serrated edge.
The Red-billed Tropicbird has a
powerful, direct flight with strong
wingbeats. It often feeds far out to sea,
plunge-diving to take prey on the
water’s surface. It also plunge-dives to
catch fish and squid, and occasionally

catches flying-fish in flight. The
species occurs in all the subtropical
and tropical oceans, although it has a
restricted distribution in the Pacific
Ocean. The Red-billed Tropicbird
has been observed

ADULT BIRD

pelicans and relatives

Phaethon lepturus

White-tailed
Tropicbird
LENGTH

70–90cm (28–35in)
WEIGHT

BREEDING
Most birds in this order nest in colonies, often on
rocky offshore islands. The largest colonies,
formed by gannets, boobies, and cormorants, can
contain hundreds of thousands of birds, with each
breeding pair spaced just beyond pecking distance
from their neighbours. Their courtship rituals are
elaborate: gannets have conspicuous “skypointing” and greeting ceremonies, while male
frigatebirds puff up their scarlet pouches like
balloons. Pelicans usually nest on the ground, like
most gannets and boobies do. Most birds in this
order produce highly dependent young. They
often feed their chicks regurgitated food, which
allows them to spend several hours fishing before
they have to return to the nest.

225–300g (8–11oz)
MIGRATION

Non-migrant
HABITAT

Tropical oceans; breeds on islands and atolls

Although the White-tailed Tropicbird
has similar elegant white tail streamers
– up to 45cm (171/2in) long – to the
Red-billed Tropicbird (above), it differs
in its yellow bill and a much larger
amount of black in the upper wing.
It is monogamous and, like other
tropicbirds, constructs its nest on the
ground, well hidden under bushes,
grass, and overhanging rocks in a wide
variety of locations, including closed
canopy forest. Nests are small unlined
scrapes, but are vigorously defended
by resident birds.
ADULT ON ITS NEST

RED-BILLED TROPICBIRD IN FLIGHT

 INTRODUCTIONS TO BIRD ORDERS AND FAMILIES

All bird orders, as well as families within the passerine
order, are described in overviews such as these. These
introductions cover the common physical and behavioural
features of the group.

Gannets, such as these
Northern Gannets, nest
in huge colonies on rocky
islets, often staining
them white with
their droppings.

Fregata andrewsi

Christmas
Frigatebird
LENGTH

90–100cm (35–39in)
WEIGHT

FEEDING TIME

PLUNGE-DIVING

Brown Boobies plunge into a shoal of
fish off the coast of Peru. Air sacs under
the skin cushion their impact.

Newly hatched
pelicans are blind
and poorly developed.
Here, a young pelican
reaches deep into its
parent’s throat for a meal
of partly digested fish.

1.5kg (31/4lb)
MIGRATION

Non-migrant
Tropical ocean; breeds in tall forest on
shore terraces of Christmas Island

HABITAT

RED LIST CATEGORY

GREAT SITES 

Throughout the world there are places that are
famous for their bird life – either in terms of its
rich variety or the sheer numbers of certain
species that congregate there. These pages
focus on a representative selection of these
places from around the world. Other sites are
described in panels within species profiles.

Critically endangered

Both male and female Christmas
Frigatebirds are mostly black with a
white patch on the underparts, but
the female also has a white collar
and a white spur extending to the
underwings. During the mating season,
from December to June, the male
displays its red throat pouch to
attract females.
The Christmas Frigatebird has the
most restricted range of the frigatebirds
and breeds only on Christmas Island,
in the Indian Ocean. Its distribution
makes it vulnerable, and its numbers
have declined as a result of forest
clearance and phosphate mining.

Fregata minor

Great Frigatebird
LENGTH

85–105cm (33–41in)
WEIGHT

1.2–1.6kg (21/4–31/4lb)
MIGRATION

Non-migrant
Tropical oceans; breeds on isolated wellvegetated islands and atolls

HABITAT

Mainly black in colour, the Great
Frigatebird has a long blue-grey hooked
bill. In the breeding season, the male’s
display is dramatic as it perches over a
suitable nesting site to present an
enormous inflated red gular (throat) sac
at passing females, continuously shaking
its wings as it does so.
With its remarkably light body, the
Great Frigatebird is among the most
aerial of all birds, rarely landing during
the day, except when breeding. Famously,
it obtains food by stealing it in flight
from other seabirds, especially boobies.
Target birds are harassed mercilessly until
they regurgitate.The proportion of
food collected in this way is probably
small, but is more important
when food is scarce.

3),(/5%44%
The flight silhouette of the Great
Frigatebird is very distinctive, with
long, narrow, pointed wings and a
deeply forked tail.Though it soars
effortlessly for lengthy periods on
thermals or flies purposefully with
powerful wingbeats, it is ungainly on
land and barely able to walk.

description of
the site’s location
245

GREAT SITES
MALE DISPLAYING ITS RED
THROAT SAC TO A FEMALE

SAINT PAUL
ISLAND
SIBERIA

BIRD SPECIES

BIRD SPECIES

NESTING IN A CROWD

/N SPOTTING A FISH UNDERWATER
THE #OMMON +INGFISHER DIVES
VERTICALLY STREAMLINING ITS BODY
BY DRAWING ITS WINGS BACK JUST
BEFORE IT FULLY SUBMERGES
5NDERWATER ITS EYES ARE COVERED
WITH PROTECTIVE MEMBRANES !FTER
CATCHING ITS PREY IT RISES VERTICALLY
BACK TO ITS PERCH

attempting to breed to the north of its
normal range, and this change in
breeding distribution may reflect
increases in sea temperatures in these
regions due to global warming.

ANATOMY

SCOOPING FOR FISH

coloured panels
provide
additional
information on
the physiology
or behaviour
of the species,
places where
it is found, or on
its relationship
with humans

$)6% &%%$).'

BIRD SPECIES

90–105cm (35–41in)

ADULT MALE

In most of its range, the Common,
River, or Eurasian Kingfisher is the only
small blue kingfisher present. It is thus
one of the most familiar of the world’s
kingfishers. It has a bright orange cheek
patch, a white throat, and a white patch
on the neck sides. Its crown and wings
are greenish blue, the back and tail
bright cobalt blue, and the underparts
bright orange. The male has a black
bill. Despite these bright colours, this
bird can be difficult to spot as it sits
motionless on a shady waterside branch.
From its perch 1–2m (31/4–61/2ft)
above the water, the Common
Kingfisher will spot a fish and dive
steeply into the water, catching its prey
to a depth of 1m (31/4ft). Where no
suitable waterside vantage point is
available, it will hover before diving.
Its prey is mainly fish up to about
12cm (41/2in) long, but the Common
Kingfisher will also take shrimps,
aquatic insects, amphibians, and
butterflies. Adults carry fish, with the
head facing outwards, in their bills, so
that the meal can easily be passed to,
and swallowed by, hungry chicks.
Chicks are fed every 45 minutes at first,
which reduces to every 15 minutes
until they are 18 days old.The nest is in
a tunnel chamber in a sandy bank, with
chicks sitting on a bed of fish-bones.

WEIGHT

MIGRATION

LENGTH

Partial migrant

22cm (81/2in)

This shy, medium-sized kingfisher has
a distinctive plumage. It has a large
bright red bill, a pale rufescent head
and underparts, violet-tinged wings
and mantle, and a contrasting azure
rump. Its legs are red. The male and
female are similar in plumage, although
the male may be brighter.
Its prey depends on its habitat. In
forests away from water, it will catch
beetles, grasshoppers, cicadas, and small
lizards. In aquatic habitats, it feeds on
mayflies, fish, frogs, and crustaceans.
The Ruddy Kingfisher is resident in
the tropical south of its range, but
migratory in the temperate north.

Marine; breeds along rocky coastlines

MIGRATION
HABITAT Still or slow-flowing water, including
streams, small rivers, canals, small lakes, and ponds

LENGTH

80g (27/8oz)

HABITAT

25–35g (7/8–11/4oz)

Sacred Kingfisher

25cm (10in)

Phaethon aethereus

LENGTH

Todirhamphus sanctus

WEIGHT

Red-billed
Tropicbird

ADULT AFRICAN
PYGMY KINGFISHER

Alcedo atthis

HABITAT Evergreen forest and temperate woodland
around streams; also in mangroves in the south

non-passerines

Dense forest, woodland, and grassland

If the profiled bird species
is judged to be Critically
Endangered, Endangered,
or Vulnerable according
the Red List of the IUCN
(International Union for
the Conservation of
Nature) (see p.67), this
information is given under
a separate heading
following the habitat
description.

Common Kingfisher
ADULT COLLARED KINGFISHER

ADULT DISPLAYING ITS WINGS

FAMILY 8

HABITAT

NORTH
AMERICA

map providing a
visual indication
of the location of
the area

ALASKA

EA

LENGTH

A Brown Pelican’s pouch balloons
outwards as it reaches underwater. As
the pouch stretches and fills, the lower
half of the bill bows outwards.

307

One of the smallest of all kingfishers,
the African Pygmy or Miniature
Kingfisher is predominantly blue and
rufous in its plumage and has an
orange bill. The juvenile has a black
bill. This kingfisher inhabits dense
forest, where it sits quietly on a perch
1m (31/4ft) above the ground, flicking
its tail or bobbing its head as it
searches for prey. It mostly takes
insects, but will also eat small lizards
and frogs. Unusually among
kingfishers, it will follow
and prey on ant swarms.

LOCATION The Bering Sea,
about 450km (280 miles)
off the coast of southwest
Alaska and 800km
(500 miles) east of Siberia.

I

Halcyon leucocephala

Grey-headed
Kingfisher

few in
terms of species, pelicans and their
FAMILY 8
relatives include some of the most
SPECIES 64
striking and varied fish-eating birds.
Pelicans fish from the surface, using an
elastic pouch attached to a giant bill. This order also includes
plunge-diving gannets and boobies, surface-diving cormorants
and anhingas, and also tropicbirds and frigatebirds, which catch
their food while on the wing. Found throughout the world on
freshwater, coasts, and the open sea, they make up an ancient
group, with a fossil history going back over 100 million years.

Migrant

HABITAT

With the distinction of having the
largest bill of any kingfisher, the Storkbilled Kingfisher is a heavy-looking
bird. Its large head and bill lend it a
top-heavy appearance. Despite its size,
however, it can be inconspicuous as it
sits quietly in the forest understorey,
watching for prey. Its main prey is fish
and crustaceans. However, it will also
use its bill to advantage in dispatching
lizards, rodents, and young birds.
It immobilizes its prey by hitting it
against a branch before swallowing.
It defends its territory aggressively,
chasing away birds as big as storks
and eagles.

DESPITE BEING RELATIVELY

MIGRATION

Non-migrant
Primary and secondary rainforest, monsoon,
and mangrove forest, and mature plantations

HABITAT

PELICANS AND RELATIVES

11–14g (3/8–1/2 oz)

MIGRATION

HABITAT Mangroves and other coastal vegetation,
sometimes penetrating inland to open areas

Non-migrant

WEIGHT

40g (17/16oz)

Partial migrant

MIGRATION

12cm (41/2in)

WEIGHT

MIGRATION

Lowland watercourses, both within deep
forest and in open country such as paddy fields

LENGTH

20cm (8in)

55–80g (2–27/8oz)

150–200g (5–7oz)

African Pygmy
Kingfisher

LENGTH

WEIGHT

WEIGHT

Ispidina picta

Yellow-billed
Kingfisher

LENGTH

35cm (14in)

Pelicans and their relatives vary greatly in the way that they feed, and in
the amount of time that they spend in the water. At one extreme,
frigatebirds spend almost all the daylight hours in their air, soaring high
over the sea. They snatch food from the surface, or from other birds, but
hardly ever settle on the water. Cormorants and anhingas are exactly the
opposite: they spend a lot of time on the surface, and can dive for several
minutes as they search for food. Between these two extremes, gannets
and boobies plunge through the surface into shoals of fish, hitting them
in a simultaneous attack. Few of the birds in this order are true migrants,
although some species, such as gannets, spend several years wandering at
sea before they eventually return to land to breed.

RED LIST CATEGORY

Syma torotoro

Collared Kingfisher

LENGTH

BEHAVIOUR

HABITAT Eucalyptus and open woodland, scrub,
forest edges, farmland, and coastal habitats

kingfishers and relatives

ORDER Pelicaniformes

From a distance, the birds in this order
seem to have little in common, apart
from the fact that they eat fish.
However, they share a number of
unusual features that suggest a
common ancestry. One of these is the
structure of their feet – uniquely among A LIFE ALOFT
birds, all four toes are connected by
Frigatebirds soar over the sea, but
webs. Nearly all species have a throat
they avoid landing on it because their
feathers become waterlogged, making
pouch, a feature that is most developed
it difficult to take off again.
in pelicans and frigatebirds. They fly
well, but move with difficulty on the
ground. Compared to other fish-eaters, pelicans and their relatives are
often large and conspicuous. The Dalmatian Pelican, for example, has
a wingspan of nearly 3m (10ft), while the Australian Pelican has the
largest bill of any bird, measuring up to 47cm (181/2 in) long.
Frigatebirds have a wingspan of up to 2.3m (71/2 ft), despite
weighing less than 1.6kg (31/4 lb).

MIGRATION

description of types of habitat in
which species is found

Todirhamphus chloris

A relatively small kingfisher, the Greyheaded or Chestnut-bellied Kingfisher
has a distinctive plumage. Its head and
breast are grey, its back is black, and its
belly is chestnut.The wings, rump, and
tail are bright blue.The male is slightly
brighter than the female.

ORDER Pelicaniformes

WEIGHT

Breeding. Areas in which
a migrant species breeds.

ADULT STORK-BILLED KINGFISHER

170

22cm (8½in)
45–65g (1½–2½oz)

Stork-billed
Kingfisher

panel shows position
of group being
described (indicated
with white line) in the
classification hierarchy

length and weight
figures are for
adult birds,
with ranges
encompassing
males and females

LENGTH

Non-breeding. Also used
to indicate ranges for
seabirds.

Pelargopsis capensis

SPECIES 64

Sacred Kingfisher

non-passerines

Pages such as the ones shown here
contain descriptions of individual
species of bird. All species profiles
contain a text description and a
distribution map, and in most cases a
photograph of the featured bird.

widely accepted
common name of
the profiled
species

Todirhamphus sanctus

N

G

S

Anchorage

R

306

scientific name
of the profiled
species

Each profile includes a map showing
the natural range of that species,
sometimes including well-established
introduced populations. Different
colours are used to indicate whether
the bird is an all-year resident, or
inhabits the area only during breeding
or non-breeding phases.

BE

SPECIES PROFILES 

DISTRIBUTION MAPS

Saint Paul Island

Saint Paul Island is the largest of the Pribilofs, an isolated group
of four islands, lying to the north of the Aleutians, a great arc
of volcanic islands strung out across the Bering Sea. This rocky
outpost in the heart of the Bering Sea hosts some of the most
important seabird colonies in the northern hemisphere. Each year
during the brief subarctic summer Saint Paul’s rugged coastline
comes to life as huge numbers of ocean-going birds return to
land to breed. For three short months its sea cliffs reverberate
with the cacophony created by tens of thousands of puffins,
guillemots, auklets, murrelets, cormorants, and kittiwakes.
WHAT TO SPOT

RED-LEGGED KITTIWAKE

Rissa brevirostris

RUDDY TURNSTONE

Arenaria interpres

CROWDED CLIFF LEDGE

Thick-billed Murres, also known as Brunnich’s
Guillemots, are the most abundant seabird on
the cliffs of Saint Paul Island, crowding the cliff
ledges during the breeding season.

selected birds
typical of the
species that can
be seen at the
site are pictured

TUFTED PUFFIN

Fratercula cirrhata

PECTORAL SANDPIPER

Calidris melanotos

BIRD SPECIES

CLIFF-TOP BREEDING GROUNDS
Saint Paul Island has sandy beaches,
coastal mudflats, craggy peaks of basalt
rock, wet bogs, and treeless rolling hills
covered with sparse tundra vegetation.
Its 105 square km (40 square miles)
remain a pristine, barely populated
environment, but it is the surrounding
ocean that makes the island so special
for birds. The cold waters around the
Pribilofs are extremely rich in nutrients
and support one of the world’s most
productive fisheries, attracting several
million seabirds from a dozen main
species, as well as whales, fur seals,
Walrus, and sea lions.
Throughout the winter, pack ice
covers the Bering Sea as far south
as Saint Paul Island. The trigger for
seabirds to begin breeding is when
rising temperatures force the ice front
to retreat north. By the height of
summer there are up to 19 hours of
daylight, giving parent birds more time
to forage for their offspring. The cliffnesting species form a complex
community, in which each species uses
a particular nesting zone. Narrow cliff
ledges are crowded with Black- and
Red-legged Kittiwakes, Northern
Fulmars, Red-faced Cormorants,
Guillemots, and Thick-billed Murres;
Crested and Least Auklets nest among
rubble at the base of the cliffs; Horned
Puffins occupy deep crevices on the
cliff-face; and Tufted Puffins dig
burrows on the cliff-top. More than
240 species of bird have been seen on
Saint Paul Island, including migratory
ducks, waders, and passerines.

FOREWORD

B

IRDS ARE NO MORE

extraordinary than any other
living organisms.Yet it is their greater familiarity
with people that can make them seem so special. They
fly, they sing, they are rich in colour and pattern, they
are animated, and they are almost everywhere, almost
always. No other group of animals can say as much
of themselves, however interesting they are.
Bird superbly illustrates what astonishing diversity
there is among birds. The male Great Bustard (page
207) holds the record for being the heaviest of all
flying birds weighing in at 1,800g (40lb). At the other
end of the scale are the hummingbirds – some of them
so small that they can easily be mistaken for insects
and the smallest of which bears an insect’s name,
the Bee Hummingbird (page 298), that weighs
less than 2g (1/16 oz).
The familiarity of Birds has lead them to be a great
source of inspiration to people throughout our shared
history. They have a powerful place in our cultures
as symbols of freedom and wisdom as well as
spirituality. And the future of the world’s 10,000
species of birds is inextricably linked to the welfare
and livelihoods of people. One in eight bird species
is threatened with extinction; the loss of even one
diminishes us all. I hope that this beautifully produced
encyclopedia will not only serve as a celebration
of birds but also strongly encourage greater efforts
to conserve them before it is too late.
DR MARCO LAMBERTINI, CHIEF EXECUTIVE, BIRDLIFE INTERNATIONAL

SOUND AND COLOUR

The Bearded Reedling (also known as
the Bearded Tit) is a beautifully coloured
inhabitant of wetlands. It usually gives
its presence away with a ping-like call.

DAYLIGHT HUNTER

Like other birds of prey, owls are accomplished
predators. Most are active at night, but the
Great Grey Owl also hunts by day. It uses its
exceptional hearing to find prey, which it can
locate even beneath deep snow.

MOVING AROUND

Some birds rely on their legs and feet
as much as their wings to move around.
Jacanas have extremely long toes that
allow them to walk on floating plants.

ORNAMENTED TOOLS

Birds have evolved bills in a vast array of
shapes, mainly to exploit different food
sources, but those of hornbills are also
adorned with impressive ornaments.

HOLDING ON

The Coal Tit belongs to the huge group of
birds called the passerines or perching
birds. A unique foot design enables
these birds to clasp even slender twigs.

BATTLE OF WITS

KEEPING OUT THE COLD

Birds have adapted to life in all of the Earth’s climate
zones. Emperor Penguins are famed for the lengths to
which they will go to protect their eggs and young from
the harsh Antarctic conditions. This chick is sitting on
an adult’s feet to reduce heat loss to the ice beneath.

Eating a diet of other animals provides birds with energy
and protein, but it often also demands ingenuity. For
example, to avoid being stung by their prey, bee-eaters
rub or thrash bees against a branch until the sting is
discharged. They will often use the same favoured perch
to both watch for prey and later disarm it.

SHIFTING POPULATIONS

At any given time, great numbers of birds
are migrating long distances to find food.
These Whooper Swans are wintering in
Japan; they breed elsewhere in Asia.

INTRODUCTION

24

introduction

BIRD ANATOMY
lungs
oesophagus

are easily confused, but there are no such
problems with birds. They are the only animals that have feathers, and
the only living vertebrates – apart from bats – that have evolved wings
and powered flight. Internally, they have a range of special features,
including hollow bones, powerful flight muscles, and a breathing
system that extracts the maximum amount of oxygen from air. Thanks
to these adaptations, some birds soar as high as passenger planes, while
others spend years on the wing before finally landing to breed.

kidney

SOME GROUPS OF ANIMALS

All birds have evolved from the same distant ancestors
and, as a result, they share the same underlying
body plan. Their skeletons contain fewer bones
than a mammal’s, and they have bills
rather than teeth and jaws. Their wing
bones are light and hollow, and end in
a three-fingered “hand”, while their legs
have a Z-like shape, with a raised ankle
joint that looks like a backward-pointing
knee. In most birds, the ribcage is compact, but the breastbone has
a large vertical flap, called a keel, which acts as an anchor point for the
muscles that power the wings. In fast or powerful fliers, such as pigeons
and doves, flight muscles can make up 40 per cent of the body’s total
weight. These muscles generate a large amount of heat, helping birds
to maintain their high body
temperature, which averages
brachioradialis
straightens
40–42ºC (104–107ºF).

heart

gizzard

liver
small
intestines
cloaca
pancreas

INTERNAL ORGANS
skull

upper
mandible

SKELETON AND MUSCLES

crop

glandular
stomach

Birds have similar body systems to
mammals, but their organs differ. Most
have a crop and a gizzard in the digestive
system, and a single opening called the
cloaca for excretion and reproduction.

SKELETON

Birds often have long and highly
flexible necks, but the rest of the
backbone is much more rigid. The
keel projects forwards from the
breastbone. Immediately above it,
the furcula, or wishbone – formed
by a fusion of the collar bones –
functions like a spring when the
wings beat up and down.

lower
mandible

air spaces

strengthening
struts

neck
vertebrae

wingtips

flexor carpi ulnaris
folds wingtip
biceps folds
wing against
body

triceps extends
wing away
from body
during flight

MUSCLE BOUND

Most of a bird’s muscles
are packed close to its
body, giving it a
streamlined shape. In
flying birds, the largest
muscle is the pectoralis
major – this produces
most of the power needed
for flapping flight.

cerebellum

pectoralis major
makes wings flap
downwards
pectoralis minor
makes wings
flap upwards

spongy bone

AIR-FILLED BONES

To save weight, many of a bird’s bones are
pneumatized, or filled with air. These air spaces
develop early in life, and are extensions of air
sacs that connect with the lungs. In the upper
arm, the bone material itself is spongy with air
sacs and the structure of the humerus is hollow,
but criss-crossed with fine struts that prevent
collapse of the delicate limb.

furcula
(wishbone)

sternum
ulna
radius

iliotibialis braces
knee and lifts leg
flexors
bend toes

cerebral
hemispheres

NERVOUS SYSTEM
INTRODUCTION

“thumb”

spinal cord

BRAIN AND
SPINAL CORD

A large part of a bird’s
forebrain is devoted to
vision. The large
cerebellum deals with
movement and balance.

To fly, birds need fast reactions, and an ability
to process rapidly changing information,
particularly from their eyes. Their brains are
well developed and, in small birds, they can
be twice as big as in mammals of a similar size.
As well as flying, birds carry out many kinds of
complex behaviour, from courtship rituals to longdistance navigation. Most of this behaviour is “hardwired” into their nervous systems, which means that it does
not have to be learned. However, birds do learn new forms
of behaviour as they grow up, and some of their instinctive
skills – such as nest building – improve with experience.

metacarpus

metatarsus

THE SKULL

Bird skulls are strong, although often
paper-thin. Seen from above, this scan
of a bird skull shows the circle of bony
plates, called the sclerotic ring, which
supports each eye.

digit

bird anatomy

DIGESTIVE SYSTEM
Some birds – such as crows and gulls – eat
anything edible that they find, but most have
specialized diets and digestive systems that
have evolved to deal with particular foods.
Because birds do not have teeth, the majority
swallow their food whole. As it goes through
the digestive system, food is stored in the
crop before passing through a twochambered stomach. The first chamber, the
glandular stomach, secretes acidic digestive
juices. The second chamber, the gizzard, has
muscular walls which contract to grind up
food. After this, nutrients are absorbed and
waste expelled. Digestive systems are
modified in different ways. Seed-eaters have
large crops, so that they can eat rapidly and
DOWN IN ONE
move on. Many seabirds also have large
Birds often have a surprisingly
crops, to allow them to carry food back to
large swallow. This Doubletheir young. The Hoatzin’s crop is enormous,
crested Cormorant is tackling a
large fish – several minutes’ work. and functions like a microbial fermentation
tank, breaking down large quantities of
leaves. Glandular stomachs are largest in birds of prey, vultures, and fisheaters. The big Lammergeier Vulture produces such powerful stomach
acids that it can digest bones thicker than a human wrist. The gizzard is
largest in birds that eat seeds and nuts: many of these swallow grit and
stones that become lodged in their gizzards, helping to grind the food.
femur

ilium

ischium

LUNGS AND BREATHING
When a mammal breathes, air flows into its lungs and back out again.
Bird lungs work differently: air flows straight through the lungs, via a
system of air sacs, before being exhaled. This one-way flow allows air
and blood to move in opposite directions, known as countercurrent. As
a result, bird lungs are more efficient at transferring oxygen and carbon
dioxide than those of mammals, so that some birds can fly at over
10,000m (33,000ft) – an altitude where a mammal would lose
consciousness. Most flying birds have nine air sacs, which connect with
air spaces in major bones. Diving birds have poorly developed air spaces,
but in some land birds – such as hornbills – they reach as far as the toes.

BREATHING CYCLE
trachea

Unlike mammals, birds take two
complete breathing cycles to
move a single breath in through
the trachea, through the lungs,
and back out of the body. When
flying, their breathing rate can
speed up by 20 times to power
the extra energy required.

cervical
air sacs

interclavicular
air sac
anterior
thoracic
air sacs

trachea

posterior
air sacs
anterior air sacs
expanding
expanding
lung

lung

abdominal
air sacs
posterior
thoracic air
sacs

tail
vertebrae

INHALATION 1

LUNGS AND AIR SACS
pygostyle

25

A bird’s lungs take up less space than those
of a mammal, but they are much more
efficient. Air sacs act as reservoirs. Unlike
the lungs, they do not absorb oxygen.

At the start of the cycle, the forward and rear
air sacs expand. Inhaled air travels through the
bird’s trachea and into the rear air sacs.
anterior air sacs
compressing

posterior
air sacs
compressing

REPRODUCTIVE
SYSTEM
ribs

fibula
external
digits
(fused
together)

pubis

All birds reproduce by laying eggs. Apart from
mound-builders, or megapodes, all of them
incubate their eggs by sitting on them, and play some part in caring for
their young. In many birds, the reproductive system follows an annual
rhythm, switching on at the beginning of the breeding season, and then
shrinking again when its work is done. Female birds usually have a single
ovary, which produces eggs like units on a production line.
Eggs contain all the nutrients that a developing embryo
needs, but they do not start to develop until the eggs
are laid, and incubation begins.

EXHALATION 1

Both sets of air sacs are now compressed, so
that air is squeezed out of the rear air sacs
and into the lungs.
anterior air sacs
expanding

posterior
air sacs
expanding

MATING BEE-EATERS
INHALATION 2

The air sacs expand again, drawing more air in
through the trachea. Meanwhile, air already in
the lungs moves into the forward air sacs.
anterior air sacs
compressing

posterior
air sacs
compressing

tarsus
EXHALATION 2

To finish the double cycle, the air sacs are
compressed, driving the air in the forward air
sacs back out through the trachea.

INTRODUCTION

tarsometatarsus

In birds, as in mammals,
eggs are fertilized inside
the female’s body. In some
species, the female can
store the male’s sperm for
several weeks.

26

introduction

VISION

SENSES
starts life, it depends on its
senses to survive. For all birds, vision is the key external
sense, and one that uses up a large proportion of the
brain’s processing power. Hearing is also important, but
for most bird species – apart from notable exceptions
such as kiwis – smell and taste are not nearly as
significant as they are for us. Specialized navigational
senses, on the other hand, are vital tools for
migrant species, while the sense of balance
is essential for all birds, particularly when
they are in the air.

FROM THE MOMENT A BIRD

Birds have excellent colour vision, and they can be up to three times
better at picking out detail than humans. Their eyes often take up a large
amount of space in the head, but they differ widely in their shape and
positioning. Some bird eyes are spherical, but others are tubular, or even
conical, flaring out inside the skull. In many birds they face sideways,
but in owls and birds of prey they face forwards, giving a relatively large
field of binocular vision. In birds, visual perception differs from our
own. Birds are particularly good at spotting movement, but even in the
open, they can fail to register motionless predators or prey.
field of
monocular
vision

field of
binocular
vision

KEEPING TRACK

Compared to humans, birds have very large
eyes, but theirs are not as mobile as ours.
To follow a moving object, an owl has to turn
its head – highly mobile vertebrae allow its
neck to turn through 180 degrees.

ALL-ROUND VISION
MONOCULAR VISION

A wader’s sideways-facing eyes give it a 360
degree field of view. Most of this field is
monocular, with little sense of depth.
field of
monocular
vision

Sitting on its eggs, a Eurasian Oystercatcher
has a complete view of its surroundings, so
it is hard for predators to attack by surprise.
This kind of vision is found in many birds.

field of
binocular
vision

BINOCULAR VISION

FORWARD FOCUS

An owl’s eyes face forwards, so their fields
of view partially overlap. This overlap allows
owls to judge distances very accurately,
an important aptitude for a night hunter.

Like all birds, this Northern Goshawk has a
sensitive area, called a fovea, at the centre
of each retina. Some birds of prey have two
foveae, while terns and swallows have three.
optic nerve
iris
cornea

AVIAN EYES

Bird eyes have an adjustable iris, and
a flexible lens that focuses light on the
retina. The most sensitive part of the retina
is the fovea – a central area packed with
light receptors. Day-active birds have
spherical or flattened eyes, but owl eyes
are tubular, opening out inside the head.
The surface of the eye is cleaned by the
nictitating membrane, or “third eyelid”,
which flicks horizontally across the eyeball.

INTRODUCTION

!6)!. ).4%,,)'%.#%
"IRDS ARE FAR FROM STUPID ALTHOUGH
MUCH OF THEIR BEHAVIOUR IS INSTINCTIVE
RATHER THAN LEARNED )N CAPTIVITY
SEVERAL SPECIES ¨ NOTABLY CROWS AND
PARROTS ¨ DEMONSTRATE GOOD PROBLEM
SOLVING SKILLS "IRDS ALSO HAVE A GOOD
SPATIAL MEMORY WHICH IS PARTICULARLY
WELL DEVELOPED IN NUTCRACKERS AND
JAYS WHICH STORE FOOD IN HIDDEN
ªCACHES« FOR LATER USE
INTELLIGENCE TESTS

Laboratory tests show that many birds
quickly learn to relate particular colours or
shapes with the promise of food.

flexible
lens

fovea

senses

27

HEARING
Like their reptilian ancestors, birds lack external
ears; some owls have feathery ear tufts, but these
have little or nothing to do with hearing. A
bird’s ear openings are typically funnel-shaped,
and are hidden beneath its plumage, behind and
below each eye. In general, bird hearing is not
much more acute than our own, but some birds
have special abilities linked to the way they live.
Barn owls, for example, are unusually sensitive to high frequencies,
allowing them to home in on rustling sounds produced by small
mammals after dark. Birds are also extraordinarily good at sound
recognition. Even when dozens of different species are singing,
songbirds can instantly pick out the calls of their own kind. Birds that
nest in large colonies – such as gannets and shearwaters – show even
greater discrimination. They often pinpoint their partners solely by their
calls, although thousands of other birds may be calling at the same time.

HUNTING BY HEARING

A Barn Owl’s heart-shaped face helps to
channel sound to its ears. Asymmetrical ear
openings help the owl to pinpoint the source
of the sound with accuracy.
BALANCING ACT

Standing on one leg is a simple matter for
this flamingo, even when fast asleep. Like
mammals, birds maintain their balance
using fluid-filled cavities of the inner ear.

SMELL AND TASTE
tubular
nostrils

For many birds, the chemical senses – smell and taste – play a relatively
minor part in daily life. Most terrestrial birds have a poor sense of smell,
and birds generally judge food by its appearance, rather than by its taste.
They also have remarkably few taste buds: parrots have about 350, and
blue tits just 24, compared with about 10,000 in humans. However, as
with hearing, smell and taste are much better developed in some groups
of birds than others. New World vultures can locate dead remains by
their smell, and tubenoses (albatrosses and their
relatives) use smell to track down food on the open
sea. Kiwis also sniff out their food, using nostrils at
the tips of their bills. Honeyguides can smell beeswax
– an ability that helps them to track down the bees’
nests that supply their food.

A NOSE FOR FOOD

SUBTERRANEAN SCENT

With long tubular nostrils, the Southern Giant
Petrel can locate food by day or by night
while out at sea. Tubenoses are particularly
attracted by the smell of floating animal fats.

Kiwis are the only birds that have nostrils at
the tips of their bills. They also have highly
developed olfactory bulbs – the part of the
brain that manages the sense of smell.

NAVIGATIONAL SENSES
Birds have a remarkable ability to find their way –
whether they are close to home, or on long-distance
migrations. On home ground, most birds find their
way by sight, but a handful of cave-nesting birds use
echolocation to navigate in total darkness. Like bats and
dolphins, they emit short bursts of sound, and then listen
for the echoes that bounce back. Migrating birds use a
wide variety of sensory cues to find their way to their
destination. One of these is the direction and strength
of the Earth’s magnetic field. This sense is still poorly
understood, but it seems to involve specialized proteins
in a bird’s eyes, and tiny specks of the mineral
magnetite, which are found in a bird’s
cranial nerves (see also Migration, p.58).

SECRET SENSES

During their migration flights, geese, such
as these Barnacle Geese, make use of a
constant stream of sensory data to navigate.
Vision, hearing, and even smell may play
a part, together with their ability to sense
the Earth’s magnetic field.

ECHOLOCATION

INTRODUCTION

Oilbirds roost and nest
deep in caves in Central
and South America.
Using echolocation,
an Oilbird can navigate
its way through 500m
(1,650ft) of winding
stone passages
between its nest and
the cave mouth.

28

introduction

FEATHERS

STRUCTURE AND TYPES
OF FEATHER

versatile body covering in
the animal world. Even in the coldest habitats, they
keep birds dry and warm, and, significantly, they enable
birds to fly. Individual birds can have up to 25,000
feathers, but to stay airworthy, the majority of species
replace most of their plumage at least once a year.

Feathers are made of keratin, the same protein found in human
fingernails. The most important part of a feather is the hollow shaft,
which is anchored in the skin. The base of the shaft is bare, forming the
feather’s quill, but in most feathers, the rest of the shaft has two rows of
parallel branches, or barbs, arranged on either side. In down feathers, the
shaft is often short, and barbs are loose and fluffy, creating a layer of
insulation next to the bird’s skin. In contour feathers, the barbs are stiffer,
and they are locked together by microscopic hooks, creating a smooth
surface known as a vane. Most of a bird’s contour feathers
are arranged like roof tiles, giving its body a streamlined
shape. However, on the wings and tail, some are specially
developed, with extra-large vanes. These are a bird’s flight
feathers – the unique feature that separates birds from
their reptilian ancestors, and which enables them to fly.

FEATHERS ARE THE MOST

TYPES OF FEATHER

Down feathers are short,
and they often lack a vane.
Typical contour feathers have
a downy base, with a vane
extending to the feather’s tip.
Flight feathers have a large
vane that is often highly
asymmetrical – a shape that
helps to generate lift.

FLIGHT
FEATHER

CONTOUR
FEATHER
hooked
barbule

INTRODUCTION

DOWN
FEATHER

barbule with
no hooks

parallel barbs

WHOOPER SWAN PREENING

Feathers are one of the most prominent
features of a bird’s anatomy. Through
the processes of moulting or preening,
feathers can change a bird’s colour and
markings, and even its apparent size.

FEATHER STRUCTURE

A contour feather’s many barbs lock
together with struts called barbules.
Those that point to the feather’s tip
have tiny hooks that mesh with the
facing barbules on the next barb.

feathers

29

FEATHER FUNCTIONS
A bird’s feathers are vital to conserve body heat, particularly in small species
that endure cold winters. For example, Boreal Chickadees have a body
temperature of about 42ºC (107ºF), and they manage to keep it at this level
even when the winter air plummets to -35ºC (-31ºF), which is an amazing
achievement for a bird that weighs less than 10g (1/3 oz). Feathers also help
to keep birds dry. Contour feathers are naturally
water-repellent, but many swimming birds go one
step further and make them fully waterproof by
coating them with oil from their preen glands.
Feathers can also function as camouflage, or as
visual signals, helping to attract a mate. Moulting
and feather wear enable the same bird to look
strikingly different at different times of year.
A bird’s plumage is also highly sensitive to touch:
in many species, this sense is accentuated by hairlike feathers called filoplumes, which are thought
to detect movement of the other feathers around
them. Some birds have stiff, vaneless feathers
resembling bristles. Nightjars use these to sweep
flying insects into their mouths,
while in ostriches and hornbills,
they function like eyelashes.

KEEPING WARM

By fluffing out its
feathers, a bird
can improve its own
insulation. This female
Red-winged Blackbird has
its feathers fully fluffed,
giving it a plump outline.

BREEDING DISPLAYS

In many bird species, the males
grow highly elaborate feathers
for use in courtship rituals. This
male Great Egret is showing off
the long, extremely fine plumes
that normally lie flat on its back.

PLUMAGE
DEVELOPMENT

TREE SWALLOW NESTLINGS

MOULTING PENGUIN

These chicks are starting to grow their
feathers. Like most birds, their
plumage grows in defined areas called
feather tracts, separated by bare skin.

Halfway through its first moult, this
young King Penguin looks distinctly
unkempt. Its brown juvenile down is
replaced by waterproof adult plumage.

As a bird grows up, it goes through a series
of plumage changes. Altricial birds (see p.54)
often hatch naked, but rapidly grow a complete
set of down and contour feathers. Precocial
birds are better developed on hatching, and are
usually covered in down, which is later replaced
by the adult plumage. In most birds, the adult
plumage is grown and replaced on an annual
cycle. Many adult birds replace their plumage
in a “prenuptial moult”, which is the point
when male birds adopt their bright courtship
colours. When the breeding season
is over, they moult a second
time, and the male plumage
becomes more subdued.
DUST
BATHING

Feathers need constant cleaning and maintenance
to keep them in good condition. Many birds
regularly bathe in fresh water, although species
that live in dry habitats often bathe in dust
or sand instead. Throughout the day – but
particularly after bathing – a bird will preen its
feathers, arranging them correctly and wiping
them with waterproof oil from a gland near the
base of the tail. Birds that do not have preen
glands, such as hawks and parrots, keep their
plumage in good condition with specialized
feathers called powder down, which
release a fine dust that works like talc.
When birds moult, they usually shed
their flight feathers in a set pattern,
which varies from one species to
another. Most shed their wing
feathers in symmetrical pairs,
so that they can stay airborne as
moulting progresses. However,
many waterbirds moult all their
primary flight feathers at once. For
Secondary feathers moult
towards centre of inner wing
several weeks, they are unable to fly.

With all of its
feathers fluffed
out, a male Golden
Pheasant gives itself
a vigorous dusting.
Gamebirds frequently
bathe in dust, but
never in water.

&EATHERS DEVELOP FROM FOLLICLES ¨
SMALL OUTGROWTHS IN A BIRD­S SKIN
%ACH ONE DEVELOPS FROM THE BASE
UPWARDS FORMING BARBS AND
BARBULES AS IT GROWS 7HEN THE
FEATHER REACHES FULL SIZE GROWTH
COMES TO A HALT "Y THIS STAGE
THE FEATHER IS LARGELY DEAD BUT
IT STAYS ATTACHED TO THE SKIN UNTIL
MOULTED WHEN ITS WORKING LIFE
COMES TO AN END

skin

blood
vessel

muscle to raise
or lower feather

DEVELOPMENT OF A FLIGHT FEATHER

In early stages of development, flight feathers
are protected by cylindrical sheaths. These fall
away as the feathers take shape.

MOULTING PATTERN

Most songbirds shed their primary
and secondary flight feathers in two
sequences, which occur simultaneously
to minimize the impact on their flight.
Primary feathers moult from
“wrist” outwards to wingtip

shaft

feather
bud

MISSING FEATHERS

This Black Kite is in midmoult, so has gaps in its
wings where some of
its flight feathers have
been shed. Replacement
feathers are already
growing in their place.

INTRODUCTION

CARE AND RENEWAL

(/7 &%!4(%23
'2/7

30

introduction

SIZE AND SHAPE

WINGS
from five-fingered limbs,
but over millions of years, evolution has completely
transformed them for flight. They are light and flexible,
with an infinitely variable geometry, which gives the
best performance over a wide range of different speeds.
They can fold away when not in use, and their feathers
replace themselves to make up for wear and tear. Bird
wings vary hugely in size and shape, but stripped of
their feathers, they are all constructed on the same plan.

BIRD WINGS DEVELOPED

In the bird world there are many different wing shapes, which deliver a
very different performance in terms of endurance, manoeuvrability, and
speed. Gliding birds have long, narrow wings with only a slight bend at
the “elbow” – a shape that combines strength and maximum lift. Birds
that soar on thermals have broad wings, often with splayed flight feathers
resembling extended fingers. Fast fliers, such as swifts, have backswept
wings ending in a narrow point – a shape that reduces turbulence and
therefore the energy needed to stay in the air. Most songbirds have short
wings with a rounded rear edge, which gives excellent manoeuvrability.

STRUCTURE
Bird wings have an internal framework of hollow bones, anchored to
the body at the shoulder – often the biggest joint in the skeleton. Apart
from the shoulder, wings have two other main joints: one is equivalent
to the human elbow, while one nearer the wingtip is equivalent to the
wrist. These joints allow the wing to open and close, and also to swivel –
crucial for flight. The muscles that power the wings are mainly in the
chest, rather than in the wing itself. Several sets of tendons connect the
muscles to the wing bones, moving like a system of cables. When a bird
is in the air, its wings are constantly adjusted, fine-tuning the amount of
lift produced. In most birds, these adjustments control height and speed;
steering is carried out mainly by the tail. Swifts are an exception: they
can twist and turn in the air by beating each wing at a different speed.

LONG AND NARROW

POINTED AND BACKSWEPT

The Black-browed Albatross has extremely
long wings that it holds out stiffly, enabling
it to soar and glide over the sea for hours.

The Common Swift’s elbow joints are very
close to its body, and its extra-long, curving
flight feathers give narrow, pointed wingtips.

BROAD WITH SPLAYED TIPS

SHORT AND ROUNDED

“Slotted” flight feathers, separated by visible
gaps, generate extra lift in the White-tailed
Eagle and other large soaring birds.

Songbirds such as the European Greenfinch
have short, rounded wings for a rapid takeoff and plenty of manoeuvrability in mid-air.

alula
flexor
muscles

tendon

digit

biceps
muscle

primary flight
feathers

pectoral
muscle

triceps
muscle
tendon

secondary
flight
feathers

ANATOMY OF THE WING

INTRODUCTION

A bird’s wings are powered
by the large pectoral
muscles in the chest. The
biceps muscle in the wing
folds up the inner part of
the wing, while the triceps
spreads it out. Smaller
muscles control the outer
part of the wing.

FOLDED WINGS

A Western Yellow Wagtail splays its
tail while perching on a rock. Like
most birds, its wings fold into a Z-like
shape when not in use, so that they
can be held flat against the body. In
non-flying birds, such as penguins
and ostriches, wings are less flexible,
and rarely fold.

REDUCED TURBULENCE

Alulas – small feathery flaps attached to
each “wrist” – are visible in this young
European Honey Buzzard. When raised like
this, the alula helps to reduce turbulence.

wings

31

WINGSPAN

LONG WINGS

Wandering Albatrosses,
shown here performing
a greeting display, are
supremely elegant fliers
at sea, where their
remarkable wingspan
enables them to glide
with barely a wingbeat.

SPECIES

WING LOADING (g/cm2)

Leach’s Petrel

0.11

Barn Swallow

0.14

Barn Owl

0.29

Golden Eagle

0.71

Mute Swan (below)

1.66

The largest flying bird ever was
an extinct species called Argentavis
magnificens, which lived 12–5 million
years ago and had a wingspan of up to
8m (26ft). Today, the absolute record is held
by the Wandering Albatross, which has
a wingspan of up to 3m (10ft). On land,
the title is held jointly by the Andean
Condor and Marabou Stork, which share
a maximum wingspan of just below 3m
(10ft). At the other end of the scale, the SHORT WINGS
The Ruby-throated
Bee Hummingbird of Cuba has a tiny
Hummingbird has tiny
wingspan of just 3cm (11/5 in) – far
wings that give superb
agility and flexibility.
smaller than many insects.

WING LOADING
Although larger birds have larger wings, wing area and body weight do
not increase in step. Instead, large birds typically have a greater wing
loading, meaning that each unit area of wing has to carry more
weight. Wing loading affects a bird’s manoeuvrability and the
amount of energy it requires to fly. The greater the wing
loading, the harder birds have to work, unless they soar
or glide. In the most extreme cases, including swans,
bustards, and turkeys, taking off is a real struggle and
the birds flap hard for
several seconds to
get into the air.

WING LOADING

The table above shows the
wing loading for different
birds of varying weight. Mute Swans weigh up to 15kg
(33lb) and are among the heaviest of all flying
birds. They need a long “runway”
to become airborne.

FLIGHTLESS BIRDS
MULTI-PURPOSE WINGS

Although ostriches cannot fly, they use
their well-developed wings for displaying,
and for temperature control, exposing or
covering up the bare skin on their legs.

FLYING UNDERWATER

Penguins have stiff, compact wings that
are highly effective flippers, allowing
these Gentoo Penguins to reach speeds
of over 25kph (16mph) under water.

INTRODUCTION

If flight is no longer a great advantage to
a bird, evolution can gradually make wings
smaller, until flight is no longer possible.
At least 13 bird orders, including ostriches,
kiwis, grebes, penguins, auks, pigeons, and
even parrots, contain species that have
become flightless. In penguins and auks, the
wings are well developed and are used like
flippers for propulsion in water. By contrast,
the wings of kiwis are so tiny that they are
invisible under their plumage and have no
function. Flightlessness is most common
among birds that live on oceanic islands,
where there are no mammalian predators. In
the rail family, over a quarter of island species
cannot fly. One of them, the Inaccessible
Island Rail, is the world’s smallest flightless
bird, weighing just 30g (1oz). Many similar
species have become extinct following the
introduction of cats and other predators.

32

introduction

FLIGHT
huge advantages, particularly in the search
for food. Over millions of years, it has evolved independently in several different
groups of animals, including flying reptiles called pterosaurs, whose leathery wings
were up to 12m (40ft) across. Today, the animal kingdom includes many species that
can glide, but only three kinds of animal – birds, bats, and insects – can stay airborne
by flapping their wings. Of these, insects are by far the most numerous, but birds lead
the field in speed, endurance, load-carrying capacity, and total distance flown.
THE POWER OF FLIGHT GIVES ANIMALS

lift

FLIGHT FORCES

airflow

Flapping flight is a highly complex form of
movement, which is still not fully understood.
However, the basic principles behind bird flight are
well known. Like aircraft, birds have to generate two
forces to fly. The first, known as lift, counteracts the
downward pull of Earth’s gravity. The second force,
called thrust, counteracts air resistance or drag, and
pushes the bird forwards. In both birds and aircraft,
lift is produced by the stream of air moving over the
curved surfaces of the wings, while in most birds
thrust is produced by flapping. However, bird wings
are highly flexible, and so flapping flight can involve
many other factors as well. For example, pigeons
generate extra lift by bringing their wings together
on the upstroke, while hummingbirds can generate
a constant downdraught by making each wing trace
a path like a figure 8. Gliding birds (see p.34) are quite
different: they exploit the air currents around them,
saving much of the energy required in flapping flight.

drag
bird’s wing
thrust

gravity

WING AERODYNAMICS

Seen in cross-section, a bird’s wing forms a shape called an aerofoil.
Air moves over the upper surface faster than the lower one, causing
a reduction in pressure that results in lift. If lift is greater than the pull
of gravity, the bird rises, and if thrust exceeds drag, it accelerates
forwards. But if each pair of forces is balanced, the bird stays
at the same height and speed.
wings point
forwards while
rising from
downstroke

TAKEOFF AND LANDING

INTRODUCTION

Body weight has a far-reaching effect on the way birds take off
and land. Small songbirds can take off in a split-second with just
a kick of their legs, but heavily built birds take much longer to
get into the air. Pheasants and other gamebirds are a notable
exception to this rule: powerful flight muscles give them an
explosive take-off to escape from danger. Taking off can be
hard work, and in heavy birds, the wing’s geometry changes
to maximize lift and minimize energy-wasting turbulence.
These changes are reversed once the bird is in the air.
Landing requires careful coordination, and also plenty
of space in the case of heavy birds such as bustards and
swans. When birds land, they increase the angle of
their wings, like an aeroplane lowering its flaps.
The bird then swings its legs forwards, and if all
goes to plan, it lands on them without toppling
over. But for a heavy bird, such as a swan,
it is very difficult to lose so much
momentum in a short time. Instead,
swans land on water, using their
large webbed feet as brakes.
LIFTING OFF

When birds take off, their wing