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BIRDSBIRDS

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Contents

The Nature of Birds

The Art of FlyingPage 22

The Lives of BirdsPage 40

Diversity andDistributionPage 62

Humansand BirdsPage 80

Welcome to the world of birds. Nomatter how you approach it, thisis a wonderful book not only for

its pictures, splendid illustrations, size,and format but also because, as you readit, you will discover secrets about theseinhabitants of the Earth, which,according to the history of evolution,came into being before humans. The textis written in a direct, easy-to-understandstyle. Most birds have a much-enviedability that has inspired poems and alltypes of experiments: they can fly. Thisenables them to see the Earth from afar,with its seas, mountains, rivers, cities,and other features. It has been estimatedthat more than 200 million birds migrateeach year, all over the planet. Many of

them fly thousands of miles, crossingdesolate deserts and windy seas to arrivein Africa or Antarctica. Some find theirway using the sun, the moon, and thestars; others follow their parents or usethe course of rivers or mountain chains asreferences. In general, smaller birdsmigrating across continents stop severaltimes to get food. It is surprising how fastthey travel, in spite of these stops: it hasbeen calculated that some small speciescover almost 2,500 miles (4,000 km) infive or six days. Several studies haveshown that carrier pigeons and white-headed sparrows, for example, can travelmore than 600 miles (1,000 km) per day.Some ducks, such as the blue-winged teal,complete their trip from Canada tocentral Mexico in about 35 days, makingseveral stops to feed along the way.

Birds never cease to amaze us,whether hiding in trees, flying overhigh mountaintops, or nesting in

Antarctica or on tall buildings.Perhaps the reason for such amazementis their behavior, which continues to be amystery to human beings, as well as thedifferences among them. It is believedthat there are approximately 9,700 livingbird species in the world—more speciesthan in any other vertebrate groupexcept for fish. Once they reachadulthood, birds' weight varies from a

mere 0.06 ounce (1.6 g), in the case ofhummingbirds, to as much as 330pounds (150 kg) for African ostriches.Even though most birds fly, there aresome—such as kiwis, rheas, andostriches—that run quickly on theground. Some birds, being perfectlyadapted to aquatic life, live in oceans,rivers, and lakes. The shape of their feetand bills varies according to theenvironment in which they live. Someaquatic species have bills modified tofilter small water particles, whereasbirds of prey have strong bent bills tohold down and tear apart their prey.What is the diet of birds based on?Because of their great diversity and widedistribution, their diets differ greatly. Ingeneral, birds eat a bit of everything,although insects are the most importantelement of their diet. They eat fruit,seeds, nectar, pollen, leaves, carrion, andother vertebrates. Most birds lay theireggs in nests. Worthy of mention is theprotective attitude that both males andfemales have toward their young. Adultbirds care for their chicks, warn andprotect them against the danger ofpredators, and guide them to safeplaces where they can live and feed. Weinvite you to investigate up close theworld of these fascinating beings thatare able to run, climb, swim, dive, andcross the skies.

A Universe of Birds

WHITE HERON (Egretta alba)A species easy to distinguish inthe proximity of rivers, lakes, andlagoons

THE SENSES 16-17

DIFFERENT TYPES OF BILLS 18-19

EXPOSED LEGS 20-21

The Nature of Birds

Many scientists maintain thatbirds descended fromdinosaurs because fossils ofdinosaur specimens withfeathers have been found.

As a group, birds have exceptionaleyesight—they have the largest eyes inrelation to the size of their bodies. Inaddition, they have very light bones,which are suitable for flight. Just like

their bills, birds' feet have also changedin accordance with the functions andparticular needs of each species. Forinstance, walking birds—like othervertebrate groups—display a marked

tendency toward having a reducednumber of toes; ostriches, for example,have only two. Some birds of prey,such as eagles, have feet that areveritable hooks.

BEYOND FEATHERS 8-9

ORIGIN 10-11

SKELETON AND MUSCULATURE 12-13

INTERNAL ORGANS 14-15

OWL (Bubo capensis)This owl is native to Africa. Itfeeds on birds and mammals.

WINE-THROATED HUMMINGBIRD

WHITE-THROATED SPARROWA small bird that lives in NorthAmerica and on the IberianPeninsula

WINGSpropel, maintain, andguide birds duringflight. They havemodified bones andcharacteristic plumage.

CHEST

SONGBIRDSPasseriformes, or passerines, formthe most numerous group amongbirds; they are characterized by awell-developed syrinx that enablesthem to emit harmonious songs andtrills and by a soft plumage of variedcolors. Because of their braindevelopment, it is believed thatpasserines were the most recentbirds to come into existence.

BIRDS 98 THE NATURE OF BIRDS

Beyond FeathersD

efining what a bird is brings to mind an animalcovered with feathers that has a toothless bill andanterior extremities morphed into wings. Other

distinguishing characteristics are that they are warm-blooded and havepneumatic bones—bones filled with air chambers instead of marrow.Birds have very efficient circulatory and respiratory systems and greatneuromuscular and sensory coordination.

FEATHERSUnique. No other livinganimal has them. Theyare appealing for theirstructure, variety, andconstant renewal.

FEETBirds walk on their toes. In general,they have three toes pointingforward and one pointing backward.

EYE

INNER EAR

TARSUS

BILLOriginates in theepidermis. It is hard

and resistant, with aconsistency similar

to that of horns.It grows

continuously,like nails andfeathers.

Variety and UniformityWe can find birds in every type of environment:aquatic, aerial, and terrestrial, in polar regions

and in tropical zones. Their adaptation to theenvironment has been very successful. Nevertheless,birds are one of the groups that display the fewestdifferences among their members.

Adaptation to FlyingSome crucial anatomic and physiologicalcharacteristics explain birds' ability to fly.

Their bodies and feathers reduce friction with theair and improve lift. Their strong muscles, lightbones, air sacs, and closed double circulatorysystem also play a role in their ability to fly.

SENSESGreat visual acuteness andwell-developed hearing

TAILThe last vertebrae merge into thepygostyle. The tail feathers developin this area.

NOSTRILS

CREST

Eye Line

Crown

Face withContrastingColors

Mask

Chin

PostocularPatch

Eye Ring

IDENTIFICATIONThere are differences in plumage andskin that make it possible to identifybirds. The bill, because of itsvariations, also helps to establish birdgroups.

NAPE

ABDOMEN

THORAX

ounce(1.6 g)

(41° C) IS THEIR BODYTEMPERATURE.

pounds

WEIGHT OFTHE LARGESTBIRD

(150 kg)

AFRICANOSTRICH

PENGUIN

UNDERTAIL COVERTS

NAILS

TOES

THIGH

FLIGHT FEATHERS

COVERTS

105.8°F

High MetabolismThe high demands of flyingare compensated by a highmetabolic rate. Birdsextract as many nutrientsfrom food as they can.

STRUCTUREBalance in movement. Abird's internal architecturecontributes to its stability.The location of its feetand wings helps toconcentrate itsweight close to itscenter of gravity.

(-60° C)THE TEMPERATUREPENGUINS CAN ENDUREIN ANTARCTICA

-75 F330

0.06WEIGHT OF THESMALLEST BIRD

The evolution of birds is a debated theme in science.The most widespread theory states that birds descendfrom theropods, dinosaurs that walked on two legs.

Fossils of dinosaur specimens with feathers have been found, butArchaeopteryx, a primitive bird that lived 150 million years ago, is theoldest relative known. Completely covered with feathers, it had a pair ofwings that enabled it to fly. However, it retained many dinosaur traits.

Origin

SPINEMovable. The cervicalvertebrae have a concavejoint like that of the theropods,not a saddle-shaped one likethat of birds.

REPTILIANJAWBONES WITHTEETH Unlike modernbirds, it did not have ahorn bill. There was atight row of sharp teethon each jawbone.

THEROPODAN REPTILEFrom the Triassic Period

ARCHAEOPTERYXFrom the Jurassic Period

PIGEONAlive Today

Archaeopteryxlithographica

lived in the Jurassic Period,150 million years ago.

Order

Suborder

Diet

Length

Height

Weight

Saurischians

Theropods

Carnivore

10 inches (25 cm)

8 to 12 inches (20-30 cm)

18 ounces (500 g)

FossilsSeveral fossil sampleswere found between

1861 and 1993. The firstone, found in Bavaria,Germany, was veryimportant because itsdiscovery coincidedwith the publication ofOn the Origin of Speciesby Charles Darwin, at atime when the searchfor evolutionary “missinglinks” fascinatedscientists. The original islocated in the BritishMuseum. Another fossil,which includes the head, is inthe Berlin Museum.

ARCHAEOPTERYX

MODERN BIRD

Brain

TOESThe foot is functionally tridactyl. Itsfirst toe (hallux), which usually pointsbackward and typically does not touchthe ground, is opposable, like that ofmodern birds (it can move in a directionperpendicular to toes II, III, and IV).

Comparisonto a Human

From Reptile to Bird

SAURIAN PELVIS Hip and femur of thearchosaurian, notavian, type

ARCHAEOPTERYX LITHOGRAPHICAGraphic Reconstruction

FURCULA(MergedCollarbone)Shaped like aboomerang,as in manytheropods

UNMERGEDMETATARSUSIn modern birds,the tarsus andmetatarsus arefused into thetarsometatarsus.

FROM ARMS TO WINGSIt had a greater range ofmotion in the upper limbsthan primitive dinosaurs.

ARCHAEOPTERYX150 million years ago

RIBSPresence of ribs inthe abdomen(gastralia), typical ofreptiles anddinosaurs

SKULLSimilar to that ofpresent-day reptilesand early theropods.The arrangement ofthe brain and earsreveals that it had agreat sense oforientation and thatit was able toperform complicatedmaneuvers.

10 THE NATURE OF BIRDS

Birds have greater mobilitythan Archaeopteryx

PIGEONmodern

Its movementswere limited by itsshoulder joint, whichwas placed forward.

VELOCIRAPTOR99 to 65 million years ago

THREE TOES WITH TALONSThe hand has threeextended fingers,each of which isequipped with astrong curved talon.

Talons forclimbingtrees

WRISTIts wrist joint wasmore flexible than thatof modern birds, a traitit shared withdinosaurs.

VERTEBRATE TAILComposed of 21 or 22 pieces.Modern birds have tail vertebraethat are fused together into asingle bone called the pygostyle.

During flight, itfunctioned as arudder. On theground, itprovided balancefor walking.

Skeleton and MusculatureB

oth lightweight and resistant, the skeleton of birds underwent importantchanges in order to adapt to flight. Some bones, like those of the skull andwings, fused to become lighter. Birds have fewer bones than other vertebrates.

Because their bones are hollow, containing internal air chambers, the total weight oftheir bones is less than that of their feathers. Birds' spines tend to be very flexible inthe cervical region and rigid near the rib cage, where a large, curved frontal bonecalled the sternum attaches. The sternum features a large keel, to which the pectoralmuscles attach. These large, strong muscles are used for flapping the wings. In contrast,running birds, such as ostriches, have more developed muscles in their legs.

SKULLLight because of the fusing of bones, the skulldoes not have teeth, a bonyjaw, or grinding muscles.

HUMMINGBIRDBecause of its adaptation tostationary flight, its pectoralmuscles can account for 40percent of its total weight.

CERVICAL VERTEBRAETheir number varies according to thetype of bird. They make the neck flexible.

EYESOCKET

CORACOIDS

FEETBirds have four toes,just like their ancestors,the reptiles.

HUMERUS

RADIUS

ULNA

CARPALBONES

KNEE

FALSE KNEE

TARSOMETATARSUS

TOES

TIBIA

Flapping WingsFlying demands an enormous amount of energy andstrength. Consequently, the muscles responsible for

flapping the wings become very large, easily comprising15 percent of the weight of a flying bird. Two pairs ofpectorals, in which one muscle of the pair is bigger thanthe other, work to raise and lower the wings. Theyfunction symmetrically and in opposition to each other:when one contracts, the other relaxes. Their placementwithin the thoracic cavity corresponds roughly to thebird's center of gravity. The motion of the wings alsorequires strong tendons.

DOWNWARD FLAP

UPWARD FLAP

1.The descendingflapping of thewings takesplace.

2.

The pectoralmusclesrelax.

1.The smallerpectoralscontract anddraw the wingsinward.

2.

Humerus

Coracoids

Legs

The largerpectoralscontract.

Thesmallerpectoralsrelax.

TendonRight Wing Left Wing

Humerus

Coracoids

Tendon

Right Wing Left

Wing

Legs

UPPER MANDIBLE OF BILLIn some species, it isflexible.

LOWER MANDIBLE OF BILLIt is flexible, allowingbirds to open theirmouths wide.

FURCULA (COLLARBONE)Known as the wishbone, itis unique to birds andresults from the fusion ofthe collarbones.

Biceps

Triceps

ExtensorMetacarpiRadialis

Flexor DigitorumSuperficialis

Tendonsthat tie themuscles tothe wing

WingsWithout a doubt, wings are the greatest adaptation of birds.Strong tendons travel through the wings and merge into thehand bones, where the feathers are attached.

LEGMUSCLES

SUPPORTPOSITION

GRASPING DEVICEWhen a bird is perched,it assumes a crouchingposition with its legsbent. This causes thetendons in its feet totighten, which pulls itstoes closed and locks itsfeet in place. Thistendon-lockingmechanism keeps birdsfrom falling off brancheswhile they sleep. Tendons

Locked Toes

GastrocnemiusPeroneusLongus

IliotibialisLateralis

SemitendinousFlexor

THE COLOR OF THE FLESHdepends on the blood circulation in the muscles: the more circulation, the redder the flesh. Flying birds have red flesh, whereas nonflying birds,such as chickens, have white flesh.

STERNUMHyperdeveloped in flying birds, the sternum's long keel facilitatesthe attachment of the pectorals.

PELVIS


PYGOSTYLEThe tail vertebraeare merged; thetail feathers areanchored to the

tail.

CARPOMETACARPUSIt is formed by the

fusion of the hand bones.

TOES

PneumaticBones

Many of a bird'sbones are

pneumatic—that is, they arefull of air instead of bonemarrow. Some bones evenhave prolongations of airsacs. The bones may look

fragile at first glance, buttheir incredible strength

comes from a networkof internal

trabeculae(spongy bonestructures),which resemblethe trusses of ametal bridge.

FEMUR

Keel

Internal OrgansB

irds in flight can consume oxygen at a rate that a well-trained athletewould not be able to withstand for even a few minutes. Because ofthis oxygen consumption, all their organs have had to adapt. The

lungs of birds, though smaller than those of mammals of similar size, aremuch more efficient. Their lungs have several air sacs that both increasethe efficiency of their respiratory systems and make them lighter. Aspecial feature of the digestive system is a crop in the esophagus,where food is stored for digestion or for feeding the young. A bird'sheart can be four times larger in relation to its body size than ahuman's in relation to its body size.


700A HUMMINGBIRD'S HEART BEATS

Rufous Hummingbird(Selasphorus rufus)

STOMACH

RelaxedVentricles

They open theatrioventricular valves.

2 ContractedVentricles

The blood enters thebloodstream.

3

TRACHEA

ESOPHAGUS

LIVER

PANCREAS

CLOACA

CECA

SMALLINTESTINE

GIZZARD

HEART

STERNUM

timesa minute.

Digestive SystemBirds have no teeth. They therefore ingest food without chewing,and their stomachs break it down. The stomach is divided into two

parts: the glandular (or proventriculus) part, which secretes acids, andthe muscular (or gizzard) part, whose muscular walls grind up what iseaten. In general, the process is very fast because flying requires a lot ofenergy, and the bird has to replenish that energy quickly. The digestivesystem ends at the cloaca, which is an excretory orifice shared with theurinary system. Birds absorb almost all the water they drink.

Respiratory SystemBirds have the most efficient respiratory system of any vertebratebecause of the great effort that flying demands. It has two small, almost

rigid lungs that are assisted by nine air sacs distributed throughout the body.The air sacs work as bellows, but they do not carry out gas exchange. Oxygenenters the bloodstream through the parabronchi, which are much like the alveoliin human lungs, in that they serve as the tissue for gas exchange. In theparabronchi, blood and air flow past each other in tiny passages. Because airflows in one direction through the lungs, and blood in the lung capillaries flowsin the opposite direction, birds can make use of all the air they inhale, much likefish can with their gills and in contrast with mammals, which cannot.

A Highly Complex HeartSimilar to that of reptiles, but having a heart with fourchambers instead of three, the circulatory system distributes

nutrients and oxygen throughout the body according to the body'sneeds. The heart's size and rate vary, depending on the bird'sweight and activities. In general, bigger birds have smaller andslower hearts. For example, the heart of a seagull on the groundbeats 130 times a minute; in flight, it beats 625 times a minute. Ahummingbird's heart can beat 700 times a minute.

The Bloodenters through

the right and leftarteries.

LeftVentricle

RightVentricle

Aorta

LeftAtrium

RightAtrium

Left SuperiorVena Cava

Right Carotid

Right Jugular

Right SuperiorVena Cava

THE AIR SACS

Lung LungAnterior airsacs withinhaled air

Air

Posterior airsacs withnew air

THE HEART'S ASYMMETRYThe left side of the heart is more developed, because it pumps bloodto the whole body. The right side pumps blood only to the lungs.

1

TYPES OF GIZZARD

1 STORAGESome birds have a crop, whichenables them to store foodand digest it later. This waythey decrease their exposureto predators.

PRODUCTIONThe proventriculus secretesthe gastric juices that initiatedigestion.

BREAKDOWNIn the gizzard, a strong andmuscular pouch, food isbroken down with the helpof swallowed stones orsand. The stones and sandplay the role of teeth.

WATER ABSORPTIONoccurs in the small intestine.Birds normally get waterfrom the food they ingest.

EXCRETIONThe cloaca expels feces mixedwith urine coming from theexcretory system.

2

3

4

5

FOOD ITINERARY

Granivorous Birdshave thick musclewalls and strongmucous membranes(or internal skin) tobreak down seeds.

Carnivorous Birdshave thin musclewalls becausedigestion takes placein the proventriculus.

TONGUEUsually short, narrow,triangular, and not verymuscular.

SYRINXMakes itpossible forbirds to sing.

Gizzard

Pancreas

Crop

Esophagus

Proventriculus

OviductCloaca

IntestinalCeca

Ureters

Liver

Small Intestine

PosteriorThoracic Air Sac

Anterior Thoracic Air Sac

Lung

Cervical Air Sac

InterclavicularAir Sac

Abdominal Air Sac

Emptyanterior airsacs

Emptyposteriorair sacs

INHALATIONThe air sacs fillup with air.

1.EXHALATIONThe lungs fill upwith air.

2.

SECTION OF THE LUNGThe reticulumformed by theparabronchifacilitates theexchange of gaseswith the blood.

THE PERCENTAGE OFTHE BODY'S VOLUMETAKEN UP BY LUNGSAND AIR SACS

20%

LUNGAlmost rigidbecause ofits structure

CROP

Air

16 THE NATURE OF BIRDS BIRDS 17

In birds, the sense organs are concentratedon the head, except for the sense oftouch, which is found all over the body.

Birds have the largest eyes with respect tothe size of their bodies. This enables them tosee distant objects with considerable precision.Their field of vision is very broad, over 300degrees, but in general they have little binocularvision. The ear—a simple orifice, but very refined innocturnal hunters—helps them notice soundsinaudible to humans, which facilitates the detectionof prey while flying. The senses of touch and smell,on the other hand, are important only to some birds,and the sense of taste is almost nonexistent.

A BA B

Binocular vision is essential for measuringdistances without making mistakes. The brainprocesses the images that each eye generatesseparately as if they were a single image. Thesmall differences between the two images

allow the brain to create a third one in depth,or in three dimensions. Hunting birds, for whichthe correct perception of distance is a life-and-death matter, tend to have eyes located towardthe front, with a wide field of binocular vision.

In contrast, birds with lateral eyes calculatedistance by moving their heads, but theyrecord a larger total field of vision to avoidbecoming prey. Owls are the birds with thegreatest binocular vision—up to 70 degrees.

NONHUNTING BIRDS'FIELD OF VISION

The lateral eyes open the fieldof vision to as much as 360degrees but reduce thebinocular field.

HUNTING BIRDS'FIELD OF VISION

Frontal eyes reduce the totalfield of vision but allow for awide field of binocular vision.

is the most developed sense in birdsbecause some flight maneuvers, as

well as the recognition of food from afar,depend on it. Birds have relatively large eyes.In most cases, they are wider than they aredeep because the lens and the cornea—which is supported by a series of scleroticbony plates—project beyond the eye socket.In hunting birds, the eyes are almost tubular.

The muscles around the eye change its shape,alter the lens, and create greater visualacuity: birds typically have a 20-foldmagnification (and sometimes, as in the caseof some diving birds, a 60-foldmagnification), in comparison with humans.Their sensitivity to light is also remarkable,with some species being able to recognizelight spectra invisible to the human eye.

Vision

The EarBirds' ears are simpler than those ofmammals: a bird's ear has no outer

portion, and in some cases it is coveredwith rigid feathers. A notable part ofthe ear is the columella—a bone thatbirds share with reptiles. The ear isnonetheless well developed, and birdshave very acute hearing; whereashuman beings can detect just onenote, birds can detect many. The ear isessential to a bird's balance, a keyfactor in flying. It is also believed thatin certain species the ear works as abarometer, indicating altitude.

LOCATION OF THE EARS

Located at different heights onthe head, the ears cause thesense of hearing to occur with aslight delay. In nocturnal hunters,such as owls, this asymmetryallows for the triangulation ofsounds and the tracking of preywith a minimal margin of error.

Touch, Taste, and SmellThe sense of touch is well developed in the bill andtongue of many birds, especially in those birds that

use them to find food, such as shore birds andwoodpeckers. Usually the tongue is narrow, with fewtaste buds, but they are sufficient to distinguishamong salty, sweet, bitter, and acidic tastes. Thesense of smell is not very developed: although thecavity is broad, the olfactory epithelium isreduced. In some birds, such as kiwis andscavengers (condors, for example), theolfactory epithelium is more developed.

A B

A B

SCLERA

CHOROID

FOVEA

CORNEA

PUPIL

IRIS

PECTEN

EXTRAOCULARMUSCLES

RETINAEYELID

SCLEROTIC RING

The Senses

UPPERAUDITORYCAVITY

LOWERAUDITORYCAVITY

THE HUMAN FIELD OF VISION

The eyes, located at the front,move together, covering thesame area. Because humanbeings cannot move their eyesindependently from each other,they have only binocular vision.

FIELD OF VISION

The eyes—when located on thesides of the head, as is the casewith most birds—create a broadfield of vision: more than 300degrees. Each eye covers differentareas, focusing on the same objectonly when looking ahead througha narrow binocular field of vision.

COMPARISON OF BINOCULAR FIELDS OF VISION

BINOCULARFIELD OFVISION

MONOCULAR FIELDOF VISION

BINOCULARFIELD OFVISION

MONOCULARFIELD OF VISION

EXTRAOCULARMUSCLES

BIRDS 19

DifferentTypes of Bills

NOSTRIL

CULMEN

TIP

CHIN

UPPER JAW

GONYS

COMPOSITIONAND STRUCTURE

The jaws are covered with a hardhorn layer called the ramphotheca,which is the external, visible

portion. This determines thebill's color.

The beak, or bill, is a projectingstructure of horn—made out ofthe same material as the

nails—that grows as it is worndown. In the case of adult birds,bill size remains constant. The billis joined to the skull in a waythat allows for the movementof the lower mandible and,thus, the opening of themouth. Most birds depend ontheir bills to get food. Thereare many types of bills,which differ in size, shape,color, and hardness,depending on the wayin which the birdgets its food.

LOWER JAW

UPPERMAXILLARYBONE

LOWERMAXILLARYBONE

RAVENBecause of its unrestricteddiet, its bill is simple andrelatively long.

FLAMINGOFlamingos have thin, threadlike structuresinside their bills whosefunction is similar to thatof the baleen of whales.They feed onmicroorganisms throughfiltration.

TOUCANS AND ARICARIWith their long, thick bills,they can reach fruit locatedon branches that are toothin for the bird to sit on.Their bills are also used tobreak the peels and seedsof fruits.

GREENFINCHLike granivores in general,it has a strong, conical bill,used to detach seeds fromplants and, sometimes, tocrack them.

FALCONIt uses the false (tomial)tooth at the tip to detachthe flesh from the boneand to break the spine ofits prey.

HERONThe heron fishes in shallowwaters and has a long, solid,sharp bill that quickly slicesthrough the water to easilyharpoon fish.

HUMMINGBIRDThe ability to reach thebottom of a flower inorder to suck nectarrequires not only a long,thin bill but also a specialtongue.

CROSSBILLIt feeds only on pineseeds. It uses its bill toreach the scales of pinecones, open them, andextract the pine nuts.

PREMAXILLA

DENTARYCOMMISSURE

Heterogeneous ShapesBills have a wide array of names and shapes,but they are usually classified according to

their length in relation to the head (short or long);to the curvature of its axis (pointing upward ordownward); to its width; to its general shape(conical, stiletto-shaped, or spatula-shaped); and tothe presence or absence of accessory pieces, suchas grooves, horny plates, or false serrated teeth.

There is a close relationship between abird's bill and its diet. Because the bill

serves to pick up, hunt, tear, and transportthe food, depending on the bird's lifestyle, itsappearance is related to the bird's diet. If the

diet is very specific, the bill tends to have anadapted, unique shape, as is the case withhummingbirds. Omnivorous birds, on theother hand, have simple bills with no specialalterations that are suitable for all tasks.

You Are What You Eat

Parts of the BillEach jaw has characteristic elements. In theupper one, from the back to the front, are the

nostrils (or nasal cavities), the culmen (or maxillarycover), and the tip, which, in carnivorous birds,contains the tomial, or killing, tooth. In the lowerjaw is the gonys, or cover. The variations found ineach part of the bill are conditioned by the bill'sfunction.


HardnessIts long, stout bill isextraordinarily hard. Despiteits appearance, the bill isvery light, and birds can useit adeptly to seize and toopen the fruits they eat.


Claws, Scales, and SpursThese striking foot structures play a role in finding food, movement,protection, and defense, among other things. The claws can be long

and sharp, in the case of birds of prey, or short and round, in the case ofwalking birds. Owls have a comblike claw that they use to groom theirplumage. Their scales, inherited from reptiles, help protect theirfeet. In some cases, they help the birds to move throughwater. Many birds, such as chickens, pheasants, and

crested screamers (a South American waterbird),have a spur, which they use as a

defensive or offensiveweapon.

Birds walk on their toes,which form the first portion

of their feet. The second portion isformed by the tarsometatarsus. Itstop part is connected to the tibia,through a joint similar to that of ourankle. That is why the leg flexesbackward. The knee, equivalent to

ours, is higher up and works like ahip. It is located close to the body,and it helps to maintain balance.The thigh bone also stabilizes thebody by adding weight to theskeleton. All the movements ofthese bones are controlled bytendons and muscles.

Internal/External Structure

Thigh

Knee

Knee

Thigh

Tibia

HeelTarsus andMetatarsus

MetatarsusToes

Hallux

Tarsus

FOOT

FootHeel

Tibia

TIBIAThe tibia merges into tarsal bones andforms the tibiotarsus.It has a slightlydeveloped fibula on its lateral face.

THE FOOT IIThe distal tarsal bones merge into themetatarsal bone andcreate tarsometatarsalbones.

ANKLEAlso known as afalse kneebecause it lookslike a knee thatflexes backward.In reality, it isthe ankle.

KNEE AND THIGHThe thigh is included in thebody and has a shortenedfemur. The knee is near thecenter of gravity.

Different TypesThe foot usually has four toes. Threeof them have a similar size and

position. Opposite them is a smaller toecalled the hallux. This pattern variesamong different bird groups. For example,the position and shape of toes can differ.There are even cases in which two toes arefunctional while the others have beenreduced in size. This is the case withflightless birds such as rheas. Differencesare also found in the skin, which may forma web between the toes and projections ofhorn. All these characteristics becometools to help the bird survive in itsenvironment and face challenges regardingobtaining food.

Adaptation to TreesThe common waxbillperches and sleeps on treebranches without expending muchenergy. The weight of the body alonecauses its toes to close tightlyaround the branch.

BIRD LEG HUMAN LEG

FEET DESIGNED FOR PERCHINGFound on hummingbirds,kingfishers, ovenbirds,and nightjars. They havesmall feet, withthe second,third, andfourth toesjoined together. Thismakes it possible forthem to stand still.

BIRDS 21

Exposed LegsT

aking a quick look at the extremities of birds, including their toes andclaws, can help us learn about their behavior. The skin of their legs andfeet can have some striking features. All these characteristics reveal

information about the environments in which different groups of birdslive, as well as about their diets. Scientists use these characteristicsas a basis for classifying birds. The detailed study of the anatomyof a bird's leg and foot can offer useful information. The shape andplacement of bones, muscles, and tendons make it possible to understandhow birds hold their prey or perch on branches, as well as to learn about themechanics of their movement across the ground and in the water.

Toes

SCOTS DUMPY ROOSTER (Spurs)The spurs originate inskin and bone tissues.When males fightover territory or overa female, they usetheir spurs to defendthemselves.

GREAT CRESTED GREBE (Lobed Toes)In some swimmingbirds, the toes looklike oars. They havea continuous wideborder.

FEET DESIGNED FOR SEIZINGFound on birdsof prey andnocturnal rapaciousbirds. Their feetare strong, andtheir toes end in long,curved, sharp claws.They seize prey andtransport it in flight.

FEET DESIGNED FOR WALKINGFound on herons,flamingos, andstorks. Thetoes and legsare very long. Thehallux is pointedbackward. They livein places with soft ground,such as swamps and riverbanks.

FEET DESIGNED FOR CLIMBINGFound on parrots,woodpeckers, andcuckoos. The halluxand the fourth toeare pointedbackward. Thisarrangementprovides thebirds with more strengthfor climbing tree trunks.

FEET DESIGNED FOR RUNNINGFound on bustards,curlews, and rheas. Theyhave long legs with shorttoes. The hallux andthe fourth toeare very small,which decreasescontact with the groundwhile running.

2431

FEET DESIGNED FOR SWIMMINGAlcas, patos yFound on auks,ducks, andpenguins, whichhave a membranebetween their toesthat forms a weband increases the surfaceof the foot that is incontact with the water.

TRICOLORED HERONIts feet have long, thin toes thatallow it to move on soft ground,such as in swamps, on riverbanks, and on lake shores. Itlives in the regions of Arica andCoquimbo in Chile.

THE FOOT IToes 1 (hallux)and 2 have threephalanges, toe 3has four, and toe4 has five.

BALD EAGLE(Talons)Very long, curved,pointed claws. Theyenvelop the body of

the prey andpierce it.

TO RENEW IS TO LIVE 32-33

GLIDING 34-35

FLAPPING FLIGHT 36-37

SPEED RECORDS 38-39

The Art of Flying

Birds move in the air the sameway a glider does, that is, bymaking the most of aircurrents to gain height andspeed while moving. The

shape of the wings varies accordingto the needs of each bird group.Some cover considerable distancesand thus have long, narrow wings,whereas others have short, rounded

wings that allow them to make shortflights from branch to branch. Birdsalso have shiny, colorful feathers thatmales frequently use both to attractfemales and to hide from enemies.

Feathers are usually renewed once ayear, and this process is as vital tobirds as feeding.

ADAPTATIONS 24-25

FEATHERS 26-27

WINGS TO FLY 28-29

TAIL TYPES 30-31

PARROT FEATHERDetail of the feathers worn bythese colorful aerial acrobats

There are three main theories toexplain why birds developed theability to fly. The evidence that

supports each of them tells a story ofadaptations to an aerial world inwhich the fight for food and survivalis key. One reasonable theory arguesthat birds descended from an extinct lineof biped reptiles that fed on plants and usedto jump from branch to branch to flee.

24 THE ART OF FLYING BIRDS 25

Adaptations

IS THE MAXIMUM WEIGHT AN EAGLE CAN CARRYDURING FLIGHT.

The eagle itself usually weighs about 13poounds (6 kg) and can generally carryprey weighing 6.5 pounds (3 kg). Someeagles, however, have beenn seen carryingprey estimated to weigh 13 pounds (6 kg).Carrying any more weight would requirebiggger wings, which would be moredifficult to move and less efficient. It isbelieved that large flyingg animalsdisappeared because of this limitation.

FlyingSquirrel

GLIDING SPECIES

OTHER FLYING ANIMALSIn flying animals, from primitive pterodactyls to bats,wings have always been a flap of skin. A tear createsserious problems because it takes time to heal, and thewing may be misshapen afterward.

THE BEST SOLUTIONFeathers are a unique evolutionaryadvantage. Their versatility, strength,individual nature, and ease ofreplacement make them an idealadaptation to flight forvertebrates.

THE EMERGENCE OF THE WINGIt evolved from an arm with a talon into alimb, without a talon, that was adapted forflight. The causes of this change are not yetclear to scientists. However, fossil recordsshow how bones merged until they reachedtheir present forms.

FROM SCALES TO FEATHERSThe development of feathers brought greatadvantages to birds because feathers enabledthem to fly. Feathers evolved from scales, andthey are made of the same material. Featherskeep the body's temperature constant andare lighter than scales.

EAGLEIn its maneuvers, thisgreat hunter displays theentire evolution of flight.

The tips of the wingspropel flight; the armssupport the bird; and theshoulders enable theflapping movements.

The bones areextended andreinforced; thenthey merge.

150

Today

The shoulders canperform a widerrange of movements.The fingers merge.

175

Dinosaur arm withpincer claw andlimited movement

200

RotaryShoulder

Three Fingers

MILLION YEARS AGO

MILLIONYEARS AGO

Emergence of theTarsometatarsus

CLIMBINGThe evolution ofdinosaurs yieldedclimbing species.

JUMPINGAdapted to aerial life,they jumped frombranch to branch.

GLIDINGFlight made it possible tomove from tree to treewithout using the ground.

FLAPPINGGliding wasimproved tocover distancesand increaseagility.

It is known that several evolutionary lineagesfrom both reptiles and birds did not survive the

evolutionary process, and that the lineage that trulylinks these two animal groups has not yet been found.However, some theories state that the change fromreptile to bird took place through a long process of

adaptation. There are two arguments and a variant:the arboreal theory, which posits an air-ground flightmodel; the cursory (or running) theory, which focuseson the need for stability when running; and a variant,related to parental care, which posits that dinosaursstarted to fly as a way of keeping their eggs safe.

From Reptile to Bird

RUNNINGTheir two legsenabled them torun at high speeds.

JUMPINGAs they jumped high,their wings stabilizedthem, allowing themto catch prey.

THE ARBOREAL THEORYThis theory, the most accepted for a long time, states that flight was an adaptation to

the environment in which certain herbivorous climbing reptiles lived. At first, dinosaursdeveloped a kind of parachute to protect them if they missed a branch when jumping, andlater it became a way to move from tree to tree. Finally, flight evolved to involve theflapping of wings, which allowed the animal to cover greater distances.

THE CURSORY, OR RUNNING, THEORYSupported by good fossil evidence, the running theory argues

that birds descended from certain bipedal dinosaurs that were fastrunners. Their arms opened, evolving into wings, to stabilize them as they jumped. Progression from this development to flying was simply a matter of time.

PARENTAL CARE VARIANT

This variant proposes that reptiles started to climb trees to prevent their young frombecoming prey. Gliding removedthe need to climb out of the trees.

3

2

1

4

1 SCALESResistant, theycovered the bodyof dinosaurs.

LARGESCALESSeveral dinosaurspecies had them.

3MODIFIEDSCALESThey becamedivided intosmaller sections.

FEATHERSToday found only onbirds, feathers arescales partitioned intothree smaller sections.They form a light,uniform, resistantnetwork that coversthe whole body.

FlyingGecko

LimitedShoulder

Short Arm

FiveFingers

MILLIONYEARS AGO

FLAPPINGAfter developing theability to jump andglide, these reptilesstarted flapping tocover greater distances.

HighlyMobileShoulder

26 (12 kg)pounds

2

A swelling, or papilla,develops in the bird'sskin.1

FeathersF

eathers are the feature that distinguishes birds from all otheranimals. They make birds strikingly colorful, protect themagainst cold and intense heat, enable them to move easily

through the air and water, and hide them from enemies. Feathersare also one of the reasons why human beings have domesticated,caught, and hunted birds. A bird's set of feathers is called itsplumage, and its color is essential for reproductive success.

SPECIAL FEATHERS

Vibrissae are special feathersformed by only one filament.Sometimes they have loose barbsat the base that perform a tactilefunction. They are located at thebase of bills or nostrils or aroundthe eyes. They are very thin andare usually blended withcontour feathers.

POWDER DOWN

This special type of feathercan be found on some aquaticbirds. They growconstantly and break offat the tip into small waxyscales. This “powder” ispreened into theplumage to provideprotection.


Vibrissae

Filoplumes

CALAMUSIt provides the necessary nutrients forfeathers to grow. Nerve endings thatstimulate the feather's movement arefound at its base. This allows the birdto detect changes in its surroundings.

Types of FeathersThere are three main types offeathers, classified according to

placement: those closest to the bodyare down, or underlying feathers; thoseat the top are contour feathers; andthose on the wings and tail are flightfeathers, which are often referred to asremiges (on the wings) and rectrices(on the tail).

PREENING THE PLUMAGE

Birds need to preen their feathers withtheir bills not only to keep them cleanand free of parasites but also tokeep them lubricated, which helpsbirds resist inclement weather.Birds touch their uropygial, or preen,glands with their bills. Then theydistribute the oil and wax thisgland produces all over theirplumage. This task is amatter of survival.

DUST BATH

Birds such as pheasants,partridges, ostriches, pigeons,and sparrows perform dustbaths to control the amount ofgrease on their feathers.

WHAT IS KERATIN?

Keratin is a protein that forms part of theoutermost layer of a bird's skin, just as it does inother vertebrate animal groups. Keratin is themain component of feathers, hair, andscales. Its distinct resistance helpskeep the hooklets woven togetherin the vane. This allows birds'feathers to maintain their shapein spite of the pressure exertedby the air during flight.

25,000THE NUMBER OF FEATHERSTHAT LARGE BIRDS, SUCH ASSWANS, CAN HAVE.In contrast, thenumber of featherssmall birds, such assongbirds, can have variesbetween 2,000 and 4,000.

PTERYLAE AND APTERIA

At first glance, a bird's body is covered withfeathers. However, feathers do not grow all overthe body but rather in particular areas calledpterylae. This is where the papillae, which createnew feathers, are found. The shape andplacement of pterylae vary according to species.Pterylae are surrounded by naked areas, calledapteria, in which feathers do not grow. Penguinsare the only birds whose bodies are completelycovered with feathers. This characteristic makesit possible for them to live in cold regions.

In the papilla, specialskin cells form afollicle.2

A tube that willextend from its baseand become a feathergrows in the follicle.

SELF-CLEANINGWITH ANTS

Some birds, such as certain tanagers,catch ants with their bills and grindthem. They then oil their featherswith the ground-up ants. It is believedthat the acid juices from the squashedants work as a repellent against liceand other external parasites.

StructureThe structure of feathers has twoparts: a shaft and a blade. The shaft is

called the rachis, and the part connected tothe bird's skin is called the calamus. Themovement of a feather is generated in therachis. The blade is composed of barbs thatbranch into barbules. The feather's blade, inwhich the barbules have a series of barbicels,or hooklets, at the tip, is called a vane. Theinterlocking hooklets in the vane create anetwork that adds rigidity and resistance tothe feather. It also defines the characteristicaerodynamic shape of feathers and helpsmake the feather waterproof. When featherswear out, birds have the ability to replacethem with new ones.

DOWN

These light and silky feathersprotect the bird against thecold. They have a shortrachis, or none at all. Theirbarbs are long, and theirbarbules lack hooklets. Ingeneral, down is the first typeof feather that birds developwhen they hatch.

CONTOUR

Also called covertfeathers, they are shortand rounded. They aremore rigid than downfeathers. Because theycover the body, wings,and tail, they givebirds their shape asthey fly.

INFERIOR UMBILICUSThe orifice at the base ofthe calamus, into whichthe dermic papillapenetrates. New feathersreceive nourishmentthrough it.

HOLLOWINTERIOR

IMPERIAL HERONPowder downkeeps its plumagewaterproof.

RACHISA feather's mainshaft, similar to ahollow rod

EDGEThe edge presentsan excellentaerodynamicprofile for flying.

INNER PULPOF THE SHAFT

TRAILING EDGE NOTCHThe turbulenceduring flight isreduced by thisnotch, foundnear the tip ofthe wing.

BARBSare slim, straightramifications thatgrow perpendicularto the rachis.

VANE, OR BLADEIts outer portioncontains a greatnumber of barbicels.

SUPERIOR UMBILICUSIt contains some loosebarbs. Some feathers havea secondary rachis, thehyporachis.

3

BARBS

HOOKLETS, ORBARBICELS

BARBULES

28 THE ART OF FLYING

Wings to FlyW

ings are highly modified arms that, through theirunique structure and shape, enable most birds to fly.There are many types of wings; they vary by species.

For instance, penguins, which are flightless, use their wingsfor the specialized task of swimming. Among all wings thathave existed in the animal kingdom, those of birds are thebest for flying. Their wings are light and durable, and in somecases their shape and effectiveness can be modified duringflight. To understand the relationship between wings and abird's weight, the concept of wing loading, which helps explainthe type of flight for each species, is useful.

FAST WINGRemiges are large and tight toallow for flapping; the surface isreduced to prevent excessivefriction.

ELLIPTICAL WINGSFunctional for mixed flights,they are very maneuverable.Many birds have them.

WINGS FOR SOARING ABOVE LANDWide, they are used to fly at lowspeeds. The separate remigesprevent turbulence when gliding.

WINGS FOR SOARING ABOVE THE OCEANTheir great length and small widthmake them ideal for gliding against the wind, as flying requires.

WINGS FOR SWIMMINGIn adapting to swimming, thefeathers of penguins becameshort, and they serve primarilyas insulation.

PRIMARIESThey are incharge ofpropulsion; theyare also calledremiges.PRIMARY COVERTS

They cover theremiges and, with thealula, change thewing shape at will.

LARGER FINGERSMALLER FINGER

CARPOMETACARPUS

ALULAR DIGITControls the alula, afeathered projection on thefront edge of the wing.

ULNA

RADIUS

HUMERUS

CORACOID

STERNUM OR KEEL

SECONDARIESTheir numbervaries greatlydepending on thespecies. Theycomplete thesurface.

MEDIAN WINGCOVERTSThey change thewing's lift whenthey rise slightly.

GREATER WINGCOVERTSThey create moresurface area and coverthe intersection pointof the tertiaries.

TERTIARIESTogether with thesecondaries, they createthe wing's surface.

There are many secondary feathers.

Wings in theAnimal Kingdom

Wings have always been modifiedarms, from the first models on

pterosaurs to those on modern birds.Wings have evolved, beginning with theadaptation of bones. Non-avian wingshave a membranous surface composedof flexible skin. They extend from thebones of the hand and body usuallydown to the legs, depending on thespecies. Avian wings, on the other hand,are based on a very different principle:the arm and hand form a complex ofskin, bone, and muscle, with a wingsurface consisting of feathers.Furthermore, the avian wing allows forimportant changes in form, dependingon the bird's adaptation to theenvironment.

Types of WingsAccording to the environment in which they live and the type of flight theyperform, birds have different wing shapes that allow them to save energy and

to perform efficiently during flight. The wing shape also depends on the bird's size.Consequently, the number of primary and secondary feathers changes depending onthe needs of a given species.

Flightless WingsAmong these, penguins' wings are an extremecase of adaptation: designed for rowing

underwater, they work as fins. On running birds, wings'first and foremost function is to provide balance as thebird runs. These wings are also related to courtship, asbirds show off their ornamental feathers during matingseason by opening their wings or flapping them. Wingsare also very efficient at controlling temperature, asbirds use them as fans to ventilate their bodies.

WANDERING ALBATROSS

ARGENTAVISMAGNIFICENS(extinct)

Wing Size andLoading

The wingspan is thedistance between the tips

of the wings. Together withwidth, it determines the surfacearea, which is an essentialmeasurement for bird flight. Notjust any wing can support anybird. There is a closerelationship between theanimal's size (measured byweight) and the surface area ofits wings. This relationship iscalled wing loading, and it iscrucial in understanding theflight of certain species.Albatrosses, with large wings,have low wing loading, whichmakes them great gliders,whereas hummingbirds have toflap their small wings intenselyto support their own weight.The smaller the wing loading, themore a bird can glide; the bigger,the faster a bird can fly.

Short feathers are located all over the wing.

They are wide at the base, withseparate feather tips.

The outermost primaryfeathers are shorter than the central ones.

The externalprimary feathersare longer.

BIRDS 29

LOOSE FEATHERSSometimes barbicels aremissing, and feathers on thewing come apart, creating aloose and ruffled appearance.

PRIMARY FEATHERSFlying birds have fromnine to 12 primaryfeathers. Running birdsmay have up to 16.

FUNCTIONThe wings ofostriches carryout the functionsof balancing,temperatureregulation, andcourtship.

PTERODACTYLSstill had talons, andonly one fingerextended their wings.

BATSFour fingers extendthe membrane, andthe thumb remainedas a talon.

BIRDSThe fused fingersform the tip of thewing where therectrices, or primaryfeathers, areattached.

Hand Bones

Feathers

Hand Bones

SkinwithHair

Hand Bones

Skin

5 ft(1.5 m)

11.5 ft (3.5 m)

24 ft (7.3 m)

BIRDS 3130 THE ART OF FLYING

Tail TypesO

ver the course of evolution, birds' tail vertebrae fused intoa pygostyle, and in their place feathers of different sizes andcolors emerged. These feathers have multiple uses: they can

control aerial maneuvers during flight, work as brakes during landing,and make noise. Males also use them during courtship to dazzle andwin over females. Usually the tail is formed by rectrices that vary innumber, length, and rigidity depending on the species.

FORKED TAILFound on swallowsand frigate birds.The externalfeathers are verylong and look likescissors.

MARGINATEDTAIL Found on blue jays.The central feathersare only slightlyshorter than theexternal ones.

SQUARE TAILFound onquails. The tailis short, witheven-sizedfeathers.

GRADUATED TAIL

Found on trogonsand kingfishers.When closed, the tailhas a layered shape.

ROUNDEDTAILFound on somesongbirds. Thecentral feathersare only slightlylonger than theexternal ones.

OPEN CLOSED

Courtship DisplayThe tail feathers of the female black grouse arestraight, whereas those of the male have a

half-moon shape. They usually keep the feathersclosed and near the ground, but during the courtshipdisplays they spread them out and show them offcompletely. To finish the show, the male runs back

and forth in front of the female.

1

The Key to How It Works

The tail can perform a variety of functionsbecause of the movement and shape of the

feathers. The powerful muscles in the pygostyleprepare the plumage for courtship displays and for flight,provide balance in walking and alighting on trees, andwork as rudders for swimming.

Black GrouseLyrurus tetrix

The male is recognized by itsbluish black plumage and thered caruncle over its eyes.

OPEN CLOSED

3

OPEN

LANDING IThe plumagespreads out, andthe main axis ofthe body ispositioned parallelto the ground.

LANDING IIThe body leansbackward, and thetail closes. Thelegs prepare tograb the branch.

LANDING IIIThe spread-out tailfeathers, together with anintense flapping of thewings, make it possible forthe bird to slow down andprepare its body to land.

2Fan of Rectrices

On flying birds, it is light andaerodynamic. On tree-climbing

birds, such as woodpeckers, theplumage is rigid, which allows them touse it as a support (pointed tail). Thecoverts of male peacocks are moredeveloped than their rectrices so thatthe peacock can show them off.

RECTRICESTail feathers can wear out and fray becauseof friction during flight or by brushingagainst vegetation.

UNDERTAIL COVERTSFeathers that cover the lower part ofrectrices, protecting them against the wearand tear caused by air friction

Order ofReplacement

Many species startmolting, a process

triggered by hormones, in aspecific order. Molting startswith remiges and wingcoverts, continues withrectrices, and finisheswith body coverts. Thisgradual processkeeps the bodytemperaturestable.

WINTER PLUMAGEThe new,unpigmentedfeathers make itpossible forptarmigans to blendwith the white snow.

11

2

2

3

3

4

4

5

5

6

6

7

7

8

8

9

9

1 Renewal starts in the firstprimary remiges andspreads outward. In thesecondary remiges, itspreads in two directions.Replacement occurs whenthe new remiges are threefourths developed.

2 The wingcoverts arereplaced.

Rectrices are replaced from the centeroutward. This happens simultaneouslywith the loss of tertiary remiges.

SUMMER PLUMAGEThe feathers have deeppigmentation. This helps birdsblend in with thevegetation.

Plumage MoltingThe main function of molting is to replace worn-outplumage. It also helps the bird adapt its appearance

to the seasons and to different stages in life. The renewalcan be partial or total. Some feathers are replaced beforethe spring, when the task is to attract a partner forreproductive purposes. In the fall, before birds have tostart caring for their young, the renewal is complete. Onmost birds, molting takes place in each pteryla, following adetermined order. Penguins, however, renew all theirfeathers at the same time, within two to six weeks.

In the epidermal papilla, theformation of the new feather causesthe detachment of the worn-out one.

A papilla develops from skin cells. Theepidermal cells multiply faster than thedermal ones and form a collar-shapeddepression called the follicle.

The rapid growth of the Malpighianlayer starts to develop the newfeather. The rachis, barbs, and barbulesbecome keratinized. The vessels thatbring nutrients are reabsorbed, and theconnection with the dermic layer isclosed. Finally the protective vanebreaks, and the feather unfurls.

The papilla grows and becomes layered. Theoutermost layer is covered with keratin, whichprotects the underlying Malpighian layer (nucleusof the papilla). A group of dermal cells bringsnutrients through the blood vessels that travelalong the new feather.

The feather, now lifeless,assumes its characteristicblade shape. A residue ofdermal and epidermal cellsat the base of the follicleforms an area that willallow for replacement whenthe feather wears out.

PRIMARYREMIGES

COVERTS

SCAPULARSALULAE

SECONDARYREMIGES

RECTRICES

THE PERCENTAGE OF A BIRD'SBODY COVERED BY FEATHERSWHEN RENEWAL IS AT ITS PEAK

61%

FOLLICLE

DERMAL PAPILLAEA feather develops ineach of them.

DERMIS

EPIDERMIS

DEVELOPINGBARBS

EPIDERMALCOLLAR

BLOOD VESSELSnourish thefeathers duringtheir development.

DEVELOPINGPLUMAGE

VANE

BARBSSEASONAL CHANGEIn the high mountains, snow transforms thelandscape during winter. During this time,nonmigratory birds exchange their summerplumage for a winter one. This change helpsthem to protectthemselves frompredators.

OLD FEATHERRenewing the plumageis important because ithelps keep the bird'sbody temperaturestable. It also keeps thefeathers in place whilethe bird moves about,and it helps the bird togo unnoticed bypredators.

NEW FEATHERBEING FORMED

20 daysIS THE AVERAGE AMOUNT OF TIME THATIT TAKES FOR A NEW FEATHER TO FORM.

NEW FEATHER

1 23

45

4 Massive replacement of chest, back, andhead coverts occurs from the centeroutward. This change coincides with thesubstitution of the seventh remex(singular of remiges).

3

PTARMIGAN

32 THE ART OF FLYING

To Renew Is to LiveT

he periodic renewal of plumage is called molting. It is thereplacement of worn-out, older feathers with new ones that arein better condition. In a bird's life cycle, molting is as important

an event as migrating or caring for young. The beginning of thisphenomenon is determined by environmental factors that trigger aseries of hormonal stimuli in birds: they start to eat more and todecrease their other activities. This, in turn, causes them to gainweight through an accumulation of fat that will serve as thesource of energy for developing new plumage.

BIRDS 33

Thermal:Hot Air

Warm AirCurrent

Cold Air

1 AscentWhen birds find a warmair current, they gainheight without having toflap their wings.

2 Straight GlidingOnce the maximumpossible height isgained, the birds glidein straight paths.

3 4 AscentThey rise again whenthey encounter anotherwarm air current.

TERRESTRIAL BIRDSThey use warm, rising air currentsgenerated through convection in the atmosphere or through thedeflection of air currents against cragsor mountains. Then they glide in astraight flight path. This type of flight

is possible only during the day.

WINGLETSTerrestrial gliders usually haveseparate primary feathers (towardthe tip of the wing) that serve todecrease the noise and tensiongenerated there by the passing of air.Modern airplanes copy their design.

FLIGHT PATTERNSFlying in formation is a way for birds inflapping flight to save energy. The leaderencounters more resistance as it flies,while the others take advantage of its

wake. There are two basic patterns: “L”and “V.” The first is used by pelicans, andthe second is used by geese.

DescentThe birdsslowly glidedownward.

TakeoffUsually, a powerful jump followed by the vertical flapping of the wingsis enough to make a bird take flight. As it descends, the tip feathers

are stacked on top of each other, forming an airtight surface that helps drivethe bird upward. As the bird raises its wings to repeat the movement, thefeathers curve and open until the wing reaches its highest point. With acouple of flaps of the wings, the bird is in flight. Bigger birds need a runningstart on the ground or water in order to take off.

THE WINGIts particular shape causeslift, with its convex sideand less pronouncedconcave side.

TYPES OF GLIDING FEATHERS

CONSTANTAIRSTREAM

CONTINUOUS AIR

FASTER AIRSTREAM

LIFT

THE ENERGYSAVED BY ASEAGULL WHILEGLIDING

70%

LOWER SIDEConcave. The air covers less distance, it does notaccelerate, and its pressure does not change.

UPPER SIDEConvex. The air covers more distance andaccelerates, causing a lower pressure that“sucks” the wing upward.

PATAGIUMElastic and resistant skin covering with feathers.It is the wing's cutting edge, responsible fordividing the airstream.

Fast and StrongFlapping

During the downward movement, theprimary feathers are closed, whichprevents air from passing through.

During theupward movement in

wing flapping, the primaryfeathers open up, offering lessresistance to the air.

Ascent

InitialJump

Run

THE PERCENTAGE OF WING FLAPPING THATGEESE SPARE THEMSELVESBY FLYING IN FORMATION

14% “V” FORMATIONThe principle is the same, butthe birds form two lines thatconverge at a point. This isthe usual formation used bygeese, ducks, and herons.

2.

1.

3.

“L” FORMATIONLeaderThe leader makes the mosteffort, as it “parts” the air.

The Rest of the FormationThe other birds make useof the turbulence producedby the leader's flapping togain height, following alongbehind.

Dynamic soaringallows birds to coverlong distances in thedirection they desire.

STRONGERWIND

is the range in altitude for dynamic soaring.

Marine BirdsDynamic soaring is performed by birds with long and thin wings, such asthe albatross. These wings are designed to take advantage of horizontal

air currents, which are responsible for the formation of waves in the ocean. Theresult is a flight consisting of a series of loops as the bird is lifted upward whenit faces the wind and moved forward when it faces away from the wind. Thiskind of flight can be performed at any time.

3 to 33 feet (1-10 m)

Terrestrial GliderA large wing surface allowsit to make the most ofrising air currents atmoderate speed.

Marine GliderThin and long wings allow it to make the most of theconstant surface winds andoffer less resistance toforward movement.

SPEED OFDISPLACEMENTdepends on the strengthof the headwind.

SECONDARYFEATHERSThere are manyof these becauseof the wing'slength.

PRIMARYFEATHERSThere arefewer ofthese, asthey onlyform the tip.

The tip feathers workas airplane winglets.

MOVINGFORWARD

Airplane Wingletsare made of one orseveral pieces.

WEAKERWIND Relay

When the leader getstired, another bird takesits position.

Air


GlidingI

nvolves using air currents to fly and save energy when traveling longdistances. There are two types of gliders, terrestrial birds and marinebirds, each of which is adapted to different atmospheric

phenomena. Terrestrial birds rise on thermals (rising air currents).Marine birds make use of oceanic surface winds. Once the birdsgain altitude, they glide off in straight paths. They slowly losealtitude until encountering another thermal that will liftthem. Both terrestrial and marine gliders have wings ofconsiderable size.

The wing length of some pelicans may reach 8 feet (240 cm)from tip to tip.

Flapping FlightM

ost flying birds use flapping flight all the time. It consists of movingthrough the air as if rowing with the wings. With each flap (raisingand lowering), the wing both sustains the bird in the air and

pushes its body forward. There are different types of flapping flight anddifferent rates of flapping. In general, the larger the bird, the morepowerful and less frequent its flapping will be. Because flapping is anactivity that consumes much energy, birds have adapted a variety offlight patterns: some, like hummingbirds, always flap their wings,whereas others alternate flapping with short-term gliding. The wingshape also varies according to the bird's needs. Birds that cover longdistances have long, narrow wings; those that fly among trees haveshort, rounded wings.

21

The feet spread openbefore landing to providemore resistance and helpthe bird to slow down.

SpreadTail

Flapping Againstthe Wind

OpenWings

WIND

Sliding

WAVELIKE FLIGHT PATH

THE HEADTilted backward to bring itcloser to the center ofgravity (between the wings)and attain balance

THE LEGSremain at rest untillanding. They stay veryclose to the body.

THE CROPMade of elasticskin. It can holdfood during flight.

Landingrequires reducing speed until the bird becomes motionless andsettles. The bird faces the wind and spreads out its tail, wings, and

alulae (bastard wings, characterized by their stiffness and growth fromthe first digit), while lifting up its body and extending its legs forward toincrease the surface area in contact with the air. In addition, the birdflaps its wings intensely in the direction opposite to its flight. Everythingworks like an aerodynamic brake. Some birds—such as the albatross, withits long, narrow wings—tend to have problems slowing down. As a result,they are ungainly when landing on the ground, but on the water they areable to ski on their feet until coming to a stop.

A Specialized DesignFlapping flight is an activity that requires mucheffort. Therefore, birds must eat large amounts of

food. A migrating swallow uses 4 kilocalories (4,000calories) per 1.6 miles (2.5 km) of flight, whereas a smallmammal needs only about 0.025 kilocalorie (25 calories)to travel the same distance.

Ideal for high speeds, it consists of flappingthe wings to gain height and then foldingthem in order to descend along the flight'strajectory. Afterward the bird flaps its

wings again, making use of the inertia ofits descent to regain height. A variation ofthis type of flight involves gliding betweenflaps of the wings.

Ascent

2 RestThe bird keeps the wings near its bodyto save energy for short intervals.

Descent

1 PropulsionThe bird flaps its wings to ascend.

Flapping Wings Folded-up Wings

8

WINDMILL FLIGHT:HUMMINGBIRDSHummingbirds are able to hover in orderto suck the nectar out of flowers. Incontrast to other birds, hummingbirds'wings are attached only at the shoulders,which provides greater freedom of wingmovement, allowing the hummingbird to holditself in the air during both the upstroke and thedownstroke. The hummingbird has to flap itswings up to 4,800 times per minute duringdirectional flight and for hovering.

The wings flap 80 times persecond during normal flying.

Diagram describing themovements of the tip of thewing during flight

The wing hasshort, sturdybones; themuscles arevery powerful.

GreatManeuverability:Hummingbirds are theonly birds capable ofmoving backward.

1

2

3

4

5

67

Courtship DisplayCertain hummingbird species canflap their wings up to 200 timesper second during courtship.

1

5

6

THE BILLProjectedforward, itsaerodynamicshape decreasesthe bird's airresistance.

THE TAILSlightly curved, itworks as a rudderduring flight and asa brake duringlanding.

Muscular strength isdistributed to theentire wing, but itincreases near the tip.

The downstroke ofthe wing providespropulsion.

THE AVERAGE SPEED OF ANADULT PELICAN DURINGFLIGHT ON A WINDLESS DAY

30

UpstrokeAs the wings move upward,the remiges separate andform grooves to reducefriction. Support for thebird comes from thepatagium, a layerof skin thatanchors the feathers and coversthe bones.

STRENGTHTo gain height abovethe ground, the wingsflap in big arches in amanner that generallyproduces a lot of noise.

ANGLE OF THE WINGVariable, depending onthe wing's position. Itcloses on the downstroke.

WING STROKEThe wing acts likean oar as it trapsair and pushes thebird forward.


DownstrokeAs the wings movedownward, the remiges areforced together, and thewing moves forward a littlefor extra support. The wing

also bends at the tips topush the bird forward,as if it were rowing.

milesper hour

(50 km/h)

PEREGRINE FALCON

Speed Records


The world of birds is amazing when expressed in numbers. Most birdstravel at speeds between 25 and 45 miles per hour (40–70 km/h), butwhen diving, peregrine falcons can reach more than 200 miles per hour

(320 km/h). Many species can reach an altitude of 6,600 feet (2,000 m),although climbers have seen geese flying over the Himalayas at more than26,000 feet (8,000 m). The fastest swimmer is the Gentoo penguin, whichcan swim 22.4 miles per hour (36 km/h). Considering its small size, it issurprising that the Selasphorus rufus, or Rufous hummingbird, which is only4 inches (10 cm) long, carries out an extensive round-trip migration each yearfrom northern Alaska to Mexico. Here are some more incredible facts.

ALTITUDE Flying at high altitudesrequires a strengthenedcirculatory system tomake up for the scarcityof oxygen in the air.

SPEEDMost birds flybetween 25 and 45miles per hour (40and 70 km/h), butthe fastest birds canbeat the cheetah, themost famous of thefast animals.

DISTANCE IThe arctic tern travels

24,850 miles(40,000 km).It migrates from Canada andLabrador to Antarctica andthe Austral Sea. On each trip,it travels 9,000 to 12,000miles (15,000–20,000 km).

ARCTIC TERN(Sterna paradisea)

DISTANCE IIThe Rufous hummingbirdflies from northern Alaskato Mexico and back—ajourney of

6,000 miles(10,000 km/h).

ENDURANCEThe endurance recordgoes to the goldenplover, which is able tofly a distance of

1,900 miles(3,000 km)without stopping.

GOLDEN PLOVER(Pluvialis apricaria)

BLACK SWAN27,000 FEET (8,230 M)OF ALTITUDE, according to a pilot whowitnessed a flock overthe Hebrides Islands

PARROT24 MPH (38 KM/H)

STARLING38 MPH (60 KM/H)

EIDER75 MPH (120 KM/H)

STORK47 MPH (75 KM/H)

GIRAFFE30 MPH (50 KM/H)

HARE20 MPH (32 KM/H)

ELEPHANT17 MPH (28 KM/H)

ROYAL EAGLE81 MPH (130 KM/H)

ROYAL SWIFT99 MPH (160 KM/H)

SPINE TAILED SWIFT106 MPH (171 KM/H)Fastest in muscular flight.

GENTOO PENGUIN22.4 MPH (36 KM/H)Fastest swimming bird

SEI WHALE30 MPH (48 KM/H)Fastest swimmingmammal

OSTRICH45 MPH (72 KM/H)Fastest running bird

PRONGHORN55 MPH (88 KM/H)Fastest mammal overlong distances

DOLPHIN22 MPH (35 KM/H)

SAILFISH50 MPH (80 KM/H)

PHEASANT31 MPH (50 KM/H)

BAR-HEADED GOOSE28,000 FEET (8,500 M)Some climbers reportedhaving seen specimens ofgeese flying at 28,000 feet(8,500 m) over theHimalayas.

CHOUGH 29,030 FEET (8,848 M)A group of climberson Mt. Everest foundchoughs standing onthe summit.

RUPPELL'S GRIFFON VULTURE

36,870 feet(11,237 m)In 1973 a Ruppell's griffonvulture crashed into anairplane flying over theIvory Coast at this altitude.

Scale (inthousands

of feet)

200 mph(320 km/h)FASTEST BIRD WHILE DIVING

CHEETAH

65 mph(105 km/h)FASTEST MAMMALOVER SHORT DISTANCES

TUNA

62 mph(100 km/h)FASTEST SWIMMING FISH OVER SHORT DISTANCES

Scale (inmiles per

hour)

Scale (in miles per hour)

Land-Water

RUFOUS HUMMINGBIRD(Selasphorus rufus)

Air

Land

Water

Weight of Males1.1–2.4 pounds (0.5–1.1 kg)

Weight of Females1.5–3.5 pounds (0.7–1.6 kg)

Weight0.1–0.2 ounce (4–6 g)

Weight15-20 pounds(7-9 kg)

Flying Altitudecommonlyreaches 20,000feet (6,000 m).

7.9 ft (2.4 m)

DRAGONFLYThe fastest flyinginsect. It reaches

31 mph(50 km/h).

4 in

(1

0 c

m)

18–2

0 in

(45–

50 c

m)

32–45 in (80–115 cm)

BIRTH IN DETAIL 52-53

POSTNATAL DEVELOPMENT 54-55

A DIET FOR FLYING 56-57

MIGRATION ROUTES 58-59

DEFENSE STRATEGIES 60-61

The Lives of Birds

The behavior of birds is closelyconnected to the seasons. Tosurvive, birds must prepare forthe arrival of fall and winterand adjust their behavior

accordingly. Gliding over the oceans, awandering albatross, for example, cantravel anywhere from 1,800 to 9,300miles (2,900 to 15,000 km) in a single dayin search of food. When the time comes

to choose a partner, the behavior ofmales is different from that of females:males employ a variety of tactics to winover females and convince them of theirfitness. Some bird couples stay together

forever, whereas other birds changepartners every year. As for caring forchicks and building nests, in mostspecies both parents participate.

THE ANNUAL CYCLE 42-43

HOW THEY COMMUNICATE 44-45

NUPTIAL PARADE 46-47

HOME SWEET HOME 48-49

FIRST, THE EGG 50-51

PARTRIDGE EGGS (Lagopus lagopus scoticus)The female lays eggs at intervals of one to two days,and she is the one who incubates them.

New HouseWhile it preparesthe nest, its chestrests, with its skinpink and relaxed.

Sleep RegulatorThe pineal gland, or epiphysis, producesmelatonin. The level of this hormonedetermines the phases of sleep andwakefulness.

In early summer, incubation takes place. Theincrease in the amount ofdaylight coincides with thisphase of the annual cycle.

The amount of light increaseswith the beginning of spring;males use their huge throatpouches to court females.

ANNUAL CYCLE Incubation, migration, andcourtship activities varyaccording to the amount of lightavailable during each season.

+ LIGHT

- LIGHT

+LIGHT

Survival ManualBirds' most striking behaviors are associated with thereproductive season. During courtship parades, birds engage in

elaborate choreographies; there are also extraordinary fights betweenmales. The blue-footed booby, the male frigate bird, and the ruff are just afew examples of birds that engage in these behaviors. Others, such as thesnowy egret (Egretta thula), prefer to offer twigs for the construction ofthe nest. The Vogelkop bowerbird (Amblyornis inornata) builds bowers withleaves, flowers, or any other object that may help him to win over thefemale. Birds' performances are not connected only to courtship. Thekilldeer (Charadrius vociferus) fakes being wounded to defend the eggs orchicks in the nest from predators. It offers itself as easy prey by dragging awing as if it were broken. This trick shifts the danger away from the young.

Reproduction is the main activity under the controlof the hypophysis, which determines behaviors such

as finding a place to court females and mate, building anest, incubating the eggs, and stimulating unborn chicks tobreak their shells. The hypophysis is a gland in the brainthat has several functions. It receives nervous and chemical

How the Hypophysis Worksstimuli and produces hormones. These hormonesregulate the metabolic activities that cause birds'internal and external sexual organs to develop. Forexample, the gonads become enlarged, and secondarysexual characteristics, such as ornamental crests orplumes, appear.

1

2

3

IN COMBATIn the summer, male ruffs develop a

huge “ruff” and auricular feathersaround their necks. Their courtships

are violent and striking. Whencompeting for mating

territory, they strugglefiercely. Afterward

they docilelysprawl theirbodies on the

ground until thefemale chooses the

lucky one.

THE MOST IMPORTANT GLANDThe hypophysis is located in the ventral area ofthe brain, below the hypothalamus. Its secretionscontrol vital functions, from blood pressure andthe balance of water and salts in the body to theactivity of the gonads and the thyroid.

The magnificent frigate bird (Fregatamagnificens) is a large bird that livesin coastal areas. It has large wings,powerful talons, and a strong hooked

bill. During the reproductive season,it is responsible for building the nest.With its impressive appearance, itendeavors to attract a female.

SHOWING OFF

SUN

2 ParadeIt lowers its head andparades like a soldieraround the nest. Finally,it shakes its whole body.

Red ChestThe throat pouchremains inflated for several hours or until the femalechooses the mostseductive male.

1 Raised HeadIt flaps itswings andmarches,looking at the sky.

IndicatingReposeTo rest, thepelican reclinesits head andplaces its billunder a wing.

Olfactory

VENTRAL VIEWDORSAL VIEW

Cerebral Hemisphere

Optical Lobe

Optical Chiasm

Cerebellum

Medulla Oblongata

Infundibulum and Hypophysis

Hypothalamus

DANCE OF THE BLUE-FOOTED BOOBY(Sula nebouxii) The males—and, on occasion, thefemales—perform a graceful courtship danceafter marking the territory for nesting. Theysing and show off their plumage withcareful synchronization.

ENLARGED AREA

Male RuffPhilomachus pugnax

The arrival of the first daysof fall coincides with adecrease in the amount oflight. The migration seasonbegins.

BIRDS 4342 THE LIVES OF BIRDS

The Annual Cycle T

he annual cycle of seasons is like the daily cycle of night and day. Fluctuations in theintensity of light over time create a series of physiological and behavioral changes in birds,whether throughout the year or throughout the day. This biological clock is clearly reflected

in birds' reproduction and migrations. Changes in light that are detected by a bird's retinas inducethe secretion of melatonin by the pineal gland. The blood level of this hormone acts on thehypothalamus-hypophysis axis, which regulates internal processes. This is one reason why birdsstart to change their plumage and feel the need to fly to other areas.

TO THEORGANS

EXPULSION OF AIR TO THE BRONCHIThe air stored in the air sacs and lungs is expelled. As it passesthrough the syrinx (located between the bronchi and thetrachea), it vibrates the tympaniform membranes. Thesemembranes are the equivalent of vocal cords in humans.

TRACHEA

SYRINX

BRONCHI

DIVERTICULA TOTHE PNEUMATICBONES

LUNGS

AIR SACS

2

44 THE LIVES OF BIRDS BIRDS 45

How They CommunicateS

ound is an important form of expression in the lives of birds. Birds' soundscan be of two types: calls and songs. The former have a simple acousticstructure, with few notes. They are associated with coordinating the activities of

a group, establishing communication between parents and their young, and maintainingcontact between birds during migration. Songs, on the other hand, are more complex inrhythm and modulation. They are controlled by the sex hormones, primarily the malehormones. For this reason, males produce the most varied melodies. Songs are linked tosexual behavior and territorial defense. In general, birds either inherit or learn them.

THE SONG AND THE BRAINBirds have a brain that is well developed for this function.Testosterone acts on the upper vocal center of the brain, whichis in charge of memorizing, identifying, and transmitting theorders for the execution of the song.

THE PRODUCTION OF SOUND IN THE SYRINXThe participation of both the sternotracheal muscles and five toseven pairs of small internal muscles is needed for producingsounds. These muscles control the elongation and contraction ofthe syrinx, which varies the pitch of the sound. The air sac is alsoimportant because it adds external pressure, which causes thetympaniform membranes to tighten. The esophagus works like aresonating box, amplifying the sound. The articulation of thesounds occurs in the buccopharyngeal cavity. There are two typesof articulation: guttural and lingual.

Territoriality and RangeOne of the most studied functions of birds'songs is territorial demarcation. When a

bird occupies a territory, it sings to announce itsclaim to competitors, as the pipit shown to theleft is doing. When birds must share territory, asin a colony, they develop dialects (variations of

sounds produced by the species). When a bird

born and raised in one location moves, it mustlearn the dialect of the new location in order tobe accepted and participate in the community.There are also mechanical sounds produced bywing strokes, legs, and bills. In a display ofterritorial defense, the eared nightjar combinessinging with beating its wings.

HIGH VOCALCENTERIt is controlledby the centralnervous systemand orders thebird to sing.

ROBUST NUCLEUS OF THEARCHISTRIATUMIt sends theinformation to themuscles of the syrinx.

NUCLEUS OF THEHYPOGLOSSAL NERVEIt controls the motorfunctions of the syrinx.

CLOSEDMEMBRANEThe membranes closeon both sides, underpressure from theexternal muscles. Thebronchi rise slightly and also adjust themembranes.

3,400

13,430

54,050

32.8

65

59

53

65.4131.2DISTANCEFEET

COVERED SURFACESQUARE FEET

SOUND INTENSITYDECIBELS

1

3

MUSCULARACTION

PESSULUS

BRONCHIALRINGS

CB

MALE PHRASE

FEMALE PHRASE

INTRODUCTORY PHRASE PHRASE A PHRASE B

1

8

6

4

2

0

2 3 TIME (IN SECONDS)

FREQ

UEN

CY I

N K

HZ

4,000SHARE WITH HUMAN BEINGSAND WHALES THE NEED FOR

“SOMEBODY” TO TEACH THEM TO VOCALIZE (SONGBIRDS,

HUMMINGBIRDS, ANDPARROTS ARE EXAMPLES).

SIMPLE SYRINXThe tympaniformmembranes are locatedabove the place wherethe bronchi divide. Theyare moved by a pair ofexternal muscles.

A AIR ANDBRONCHIDuring breathing,the songbirdmaintainsairflow withoutaffecting theresting syrinx.

INTENSITYcan vary widely from bird to bird.The larger the territory, the greaterits reach. Its frequencies can changeas well: the lower the frequency, thegreater the coverage.

Strengthening TiesSome songbirds develop very complex singing rituals. Theduet is perhaps the most striking because it requires both a

shared repertoire and good coordination between both birds. Ingeneral, the male initiates the song with a repeated introduction;the female then alternates with different phrasing. The phrasingallows for more or less cyclical variations that make it unique. It isbelieved that this strengthens ties between the pair (asdemarcation of territory does) and serves as a stimulus forcooperative behaviors, such as nest building, in which both themale and female may participate.

TRACHEA

TRACHEA

BRONCHI

SONG-PRODUCING SYRINX

THE SOUNDThe membranesvibrate with theair current andpropagate thesound throughthe trachea until it reaches the bird's bill.

TympaniformMembrane

MUSCULAR ACTION

VIBRATIONOF THE WALL

SOUND

TYMPANIFORM MEMBRANE

BRONCHIAL RINGS

birdspecies

BBIRDS 4746 THE LIVES OF BIRDS

Nuptial ParadeF

inding a mate is not easy for any species.For birds, the exhibition of plumage withbright colors, the presentation of

offerings and gifts, and the performance ofdances and highly elaborate flight patterns aresome of the particular behaviors seen duringthis period. They are known as nuptial orcourtship displays. The male resorts to all thesestrategic gestures to attract the female's attentionand prevent her from paying attention to othermales. Some of these rituals are extremelycomplicated; others are very tender and delicate.

Monogamy or PolygamyMonogamy is the most common mating system, in whichtwo birds, one of each sex, participate, leading to the

formation of a couple. This couple can endure for a singlereproductive season or for life. Polygamy is an alternativepattern, but it is not very common. Polygamy is divided into twoclasses: polygyny, in which the male mates with severalfemales, and polyandry, in which the female mates with severalmales (and may even be able to keep them all together in aharem). In either case, one partner has the sole responsibility ofcaring for the eggs and chicks. There is also an exceptional casewithin polygamy: promiscuity. In this arrangement, a couple is notformed, and the relationship is limited to copulation.

The courtship display is directly related to reproduction cycles. It takesplace before copulation, although it can continue to occur thereafter.

TIMING

Great crested grebes (Podicepscristatus) perform incredibleaquatic dances. They bow to eachother, dive, and run through thewater side by side.

MUTUAL DANCES AND COURTSHIPS

Certain birds, such as goshawksor male northern harriers, courtthe female in flight. They ascendin the air in broad circles, onlyto let themselves fall in daring,sharp dives.

AERIAL EXHIBITIONS

Another courtship strategy isthe presentation of gifts. Maleeagles give females prey, andEuropean bee-eaters offerinsects. These offerings arecalled courtship food.

GIFTS

To find a partner, birds such as the snowyegret resort to a series of very elaboratesignals, such as songs, poses, dances,flight patterns, noisemaking, and displaysof their ornamental feathers.

DISPLAYING PHYSICAL ATTRIBUTES

Australian bowerbirds build astructure called a bower, whichthey decorate with pieces ofpaper and fabric that inevitablyattract the female.

BUILDING BOWERS

PostnuptialWith this display,the great crestedgrebe ensures thecontinuity of thepairing even afterthe eggs are laid.

PrenuptialPrenuptial courtshipstarts with territorialestablishment and thesearch for a partner,which can take placesimultaneously.

When its sexualarousal peaks, the male northernharrier (Circuscyaneus) flies in a wavelikepattern to attractthe female.

During courtship, the male northern harrierpretends to attackthe female.

A

B

Special CourtshipAvian courtship is a phenomenon that, depending on thespecies, can take the form of various rituals. Lek rituals are

one of the most intriguing forms of courtship. The males gatherin a small area, called an arena, where they perform theircourtship displays for the females. The females form a circlearound the arena and end up mating with the male that has themost striking secondary sexual characteristics. Lek is a systemcontrolled by the dominant male, who ends up mating with mostof the females (polygyny). The less experienced males will matewith only a few, or even none, of the females. For some species,lek rituals can be very intricate. At least 85 species perform thisspecial type of courtship ritual, among them manakins,pheasants, cotingas, and hummingbirds. Manakins, forexample, stand in line and wait their turn to perform.

Gray Crowned CraneBalearica regulorumTwo cranes perform acourtship danceconsisting of a seriesof impressive leaps.

Emperor PenguinAptenodytes forsteriA monogamous species.Each recognizes itspartner by its voice, andcouples will spend theirentire lives together.

IS THE SIZE OF THE TAIL OF THEPEACOCK WHEN IT UNFURLS ITS MORE THAN 200 SHININGFEATHERS AND FORMS A FAN TOATTRACT THE FEMALE.

5.9 feet(1.8 m)

Types and LocationsNests are classified according to theirshape, material, and location. They vary

depending on the amount of warmth the speciesneeds, as well as in terms of the level of protectionthey offer. The greater the pressure from predators, thehigher or better hidden a nest must be. Good examples areisolated nests resembling high platforms; nests in deepdepressions in the soil or hidden in tree trunks, which are very safeand provide good insulation; and nests made of clay, which are veryhard. The most typical nests resemble a cup and are found at variouslocations, most often between two or three high, remote branches.

LININGIt is composed of fibers, hairs,feathers, anddown. It insulatesthe eggs from thecold and helpswith incubation.

WALLSEare the mostimportantcomponent in anest's construction,and they give it itscharacteristicshape. Thematerials usedvary, depending on the habitat.

BASEThis is the nest'sfoundation, and itis the first sectionbuilt by the bird.It is solid and isusually built withbulkier materials.

StructureThe cup shape is important forpreventing eggs from rolling out and

falling. Besides making the construction ofthe nest easier, the use of differentmaterials helps make the nest sturdier, asthe smaller and more flexible pieces firm upthe base, walls, and lining of the structure.Different materials also provide moreefficient insulation, keeping warmth in andcold out during the incubation and raisingof chicks. As an added reinforcement, birdsusually make the side facing the prevailingwinds thicker and the side facing the sunthinner. Thus, the whole nest is an incubatorthat conserves energy. Finally, an exteriorfinish camouflages the nest amongbranches, hiding it from predators.

BASEThe bird gathersbranches and smallsticks on a fork to laythe foundations of thenest, setting up aplatformlikestructure. The birdthen ties it to thetree, making it sturdy.

1

WOVEN NESTSWeaver birds intertwine grassblades until they form a structure.The entrances are underneath.

BURROWSParrots and kingfishers digtheir nests in sandy riverbanks.

SEWN NESTSThe tailorbird sews two largeleaves together with grass blades.The nest is inside the leaves.

PLATFORM NESTSThe sparrow hawk gathers a largenumber of branches and assemblesa high, solid base for its eggs.

THE LITTLE MASKED WEAVERbuilds solid nests, weavingtogether leaves and grass blades.Sometimes the male buildsseveral nests before the femalechooses him.

SOME VARIATIONS

ENDThe finish includesmoss and feathers tosmooth out the interiorand provide insulationagainst the wind andcold, which makes thenest more suitable forincubation.

3

SHAPEThe bird intertwinesgrass blades, smallsticks, and hairs;fastens them; and givesthem a circular shape.As constructionadvances, the bird usesadhesive materials,such as spiderwebs.

2

How the Nest Is BuiltA cup-shaped nest is built at a fork between two or three branches. Thebird arranges twigs, grass blades, and small sticks, as if building a

platform. The bird then interlaces some of these materials with the tree to givethe nest solidity. It then interweaves the materials in a circular pattern. As thenest takes shape, lighter, more adhesive materials—such as mud,spiderwebs, caterpillar silk, and certain plant fibers—are used. Although theoutside is rough, the inside is lined with feathers for softness and warmth.In general, if both the male and female participate in the construction, afew hundred trips are enough to complete the nest. In some species, such

as weavers, males have to display a nest during courtship; in others(African black eagles, for instance), the same nest is used every year.

48 THE LIVES OF BIRDS

Home Sweet HomeM

ost birds lay their eggs in a nest, wherethey are incubated by the body heat ofan adult sitting on them. To build a

nest, the couple normally uses mudmixed with saliva, small stones,branches, and feathers. When thenest is in a visible location, the birdcovers it with lichens or loose twigsto hide it from predators. Nestshapes vary according to the birdgroup: they can take the formof a bowl, a hole in a tree(woodpeckers), or an excavatedburrow on a slope of sand or soil.There are even birds that usenests built by other species.

BIRDS S49


Birds may have inherited their reproductive method from theirpredecessors, the theropod reptiles. In general, they lay as manyeggs as they can care for until the chicks become independent.

Highly adapted to the environment, the eggs of the same specieshave varying shapes and colors. These variations help keep themsafe from predators. They also vary greatly in size: the egg of anostrich is 2,000 times bigger than that of a hummingbird.

First, the Egg

THE SHELLFormed by a solid layerof calcium carbonate(calcite), it has poresthat make it possible for the chick to breathe.Bacteria are kept out by two membranes thatcover the egg, one onthe inside and the otheron the outside.

1 OVULESThey lie in folliclesarranged like abunch of grapes.

2 DESCENTOnce fertilized,the ovule travelsdown the oviductuntil it reachesthe isthmus.

3 SHELLIn the isthmus,the shellmembranes form.

4 UTERUSThe egg becomespigmented, and theshell hardens.

5 CLOACAIt expels the egg 24hours later on average(chicken hens).

LAYINGA group of eggs laid at onetime is called a laying. Duringthe mating season, a sparrowcan have several layings. Ifsome eggs are removed, thesparrow can replace themwithout difficulty.

Light Egg

Dark Egg

SpeckledEgg

SIZEThere is no exact proportion betweenthe size of a bird and its egg.

The bill and scales of the legsharden toward the end, whenthe chick is formed andreaches a size similar to thatof the egg. At that point,rotation begins so that thechick will be positioned tobreak its shell.

4

When the chick is ready to break the shell, it is taking up allthe space inside the egg. The chick is cramped with its legsagainst its chest. This enables it to open the shell with smallmovements and with the help of a hard point at the tip of itsbill (called an egg tooth).

5

Most birds' organsare formed in thefirst hours ofincubation.

3

The egg contains an embryo in oneside of the yolk. The yolk is held inthe middle of the white (albumin) bya protein cord that isolates it fromthe outside world.

1

How It FormsBirds have only one functional ovary, the left one, which grows dramaticallyduring the mating season. The ovule can descend and form what are known

as unfertilized eggs (the type used in cooking). If the egg is fertilized, embryonicdevelopment begins. The ovule, fertilized or not, descends to the cloaca in a fewhours or days. The eggshell begins to be formed at the isthmus, through thesecretion of calcium. At first soft, the shell hardens when it comes in contact withthe air.

COLOR AND TEXTURE

ISTHMUS

CLOACA

OVULE

Outer and InnerMembranes

MembranePore

CO2 andWater Vapor

Oxygen

WASTE SAC

AIR SAC

CHORIONprotects and containsthe embryo and its food.

YOLK

YOLK SAC

ALBUMINwas consumed.

YOLKdisappears into the body.

As it feeds to grow, theembryo produces wastes thatare kept in a special sac.

2

Oval: Themost

frequent

Conical:Prevents

falling

Spherical:Reduces thesurface area

SHAPE

ALBUMIN

EMBRYOPROTEIN CORD (CHALAZA)

YOLK AND WHITEThey decrease in size.

THE PROPORTIONOF AN EGGTAKEN UP BY THE EGGSHELL

8%

Kiwi Egg

1 lb(500 g)

Chicken Hen's Egg

2 oz(60 g)

Both texture and color help parentslocate the egg.

It depends on the pressure exerted by theoviduct walls. The large end emerges first.

Breaking the ShellThis process may take from a few minutes to three orfour days, depending on the species. In general, the

parents do not intervene or help their young. When the shell isempty, they throw it out of the nest, apparently to avoidattracting the attention of predators. In species whose young

hatch with the feathers already developed, hatching isextremely important. It has been observed that the singing ofthe chicks stimulates the stragglers and delays those that havegotten ahead; it is important that they all be ready to leave thenest together.


Birth in DetailW

hen a chick is about to hatch, it starts to make itself heard from inside the egg. Thisallows it to communicate with its parents. It then starts to peck at the shell with its tinyegg tooth, which is lost after birth. Next, it turns inside the egg and opens a crack with

new perforations, at the same time pushing with its neck and legs until it manages to stick out itshead. This job demands a lot of effort and can take 30 to 40 minutes or, in the case of kiwis andalbatrosses, even three to four days. In most species, newborn chicks are blind and naked, and they can open their bills only to receive food.

BROOD PATCH

Adaptations for HatchingGetting out of the egg is an intricate operation because thespace is tight, and a chick's muscles have little vigor. Birds

count on a few adaptations, such as the egg tooth and the hatchingmuscle, to accomplish the task. The tooth is used for making thefirst perforation, which allows air into the egg. The muscle exertsthe necessary strength, while stimulating the chicken's motorfunctions to intensify the effort. Both the egg tooth and thehatching muscle disappear shortly after the eggshell is broken.

HATCHING MUSCLEIt exerts pressure against theshell and helps to break it.

For the embryo to develop, it needs constant temperatures between99° and 100° F (37-38° C). The parents ensure these temperatures bysitting on the eggs and warming them with their brood patches.

INCUBATION

ASKING FOR HELPThe chick calls for its parentsfrom inside. The reply encouragesit to continue the effort.

During incubation,some species losetheir chest feathersand increase theirnumber of bloodvessels in this area.Others pluck outtheir feathers.Direct contact withthe eggs helps keepthem warm.

CRACK IN THE EGGThe chick turns inside until itsbill targets the egg's midline.It then punctures the airsac. With a few moretries, it pierces the shell.The chick then breathesfor the first time.

1

THE CRACK EXPANDSAfter making a hole in the shell,the chick opens a crack withsuccessive pecks at other points.Air gets in and dries up themembrane, which makes thetask easier.

2

GETTING OUT OF THE EGGOnce the shell is open, thechick pushes itself out withits legs and by crawling onits abdomen. For birds thathatch without feathers, thisis more difficult, becausethey are less developed.

3

4

EGGSHELL

SHELL MEMBRANE

DURATION BY SPECIESThe incubation period varies considerably:between 10 and 80 days, depending onthe species.

PENGUINBoth males and femalesincubate. The emperor male hasa special pouch for incubation.

PIGEONFemales and malesincubate. They bothdevelop a brood patch.

ALBATROSSLacking brood patches, theparents hold the egg betweentheir feet and abdomen.

80 days62 days18 days

WHAT COMES OUT FIRST?The head usually comes outfirst, because the sharp billhelps break the shell. Mostbirds then get out of the egg bypushing themselves out withtheir legs. For wading birds andother terrestrial birds, however,the wings usually unfold first.

EGG TOOTHA protuberance on the bill thatpunctures the egg. Its presencedepends on the species.

A GREAT EFFORTGetting out of the shellrequires much energy from

the chick.THE CHICK IS BORNOnce outside the chick, almostfeatherless, looks for warmthand food from its parents. Inthe case of some birds thathatch without feathers,not all eggs hatchsimultaneously; thisbenefits the firstborn

if food is scarce.

35 minutesIS THE APPROXIMATE TIME ITTAKES A SPARROW TO COME OUTOF THE EGG.

SEQUENCE OF PECKINGBetween each sequence of pecking,the chick must take long breaks.


Chicks develop at highly variable rates after hatching.Some birds are born with their eyes open and with athick layer of down feathers. These birds can also feed

themselves. That is why they are called precocious, ornidifugous. Ducks, rheas, ostriches, and certain beach birds canwalk and swim as soon as they are born. Other species are bornnaked and develop their feathers later. They need to stay in thenest until they have sufficiently developed, so adult birds must carefor them. These birds are called nidicolous. The most helpless chicksare the young of songbirds and hummingbirds, because they needwarmth from their parents to grow strong.

Nidifugous YoungNidifugous young are fully developed at themoment of birth. They can move and even leave

the nest, hence their name (which means “fleeing thenest”). This adaptation demands more incubationtime because the chick is almost fullydeveloped at birth. This is the case withincubator birds (Megapodius freycinet),which begin their independent lives inthe outside world as soon as theyleave the shell. Ducks follow theirparents but find food on their own,whereas chickens follow theirparents, and the parents show themwhere to find food.

Nidicolous BroodsMost of these chicks are born naked, withclosed eyes and with only enough strength

to get out of their shells. They stay in the nest. Forthe first few days, they cannot even regulate theirown body temperature; they need their parents inorder to stay warm. Within one week, they have afew feathers, but they require constantcare and food. They form anumerically important group thatincludes Passeriformes (songbirds).

FOODThey need much food todevelop. The parents mustfeed them 24 hours a day.

25 hoursIt performs a fewinstinctive movements.It can barely raise itshead to ask for food.

30 hoursThe chick keeps warm withthe down that covers its body.It can walk and begins to befed by its parents.

7 to 8 daysGrowth quickens, and the firstcovert feathers appear at the tip ofthe wing. The bird leaves the nest.Its diet consists of:

15 daysIt starts to performshort flights. It reversesits diet, eating:

21 daysIt is alreadyconsidered an adult.Its flights are longer.Its diet is composed of97 percent vegetables;the rest is made up oflichens and insects.

8 daysFeathers cover the chickalmost completely, exceptaround its eyes. Its legsare well developed, andthe sparrow moves around in the nest.

10 daysFeathers covereverything, but theyare not yetdeveloped. The chickcan stay warm on itsown, and it isvoracious. Growth isvery fast.

12-15 daysDevelopment is complete, and thecovert feathers are ready forflight. All that remains is for thebird to reach adult size.

6 daysSome feathers begin tounfold, the nails areformed, and the wingscontinue to grow with thebody. It can stand up.

4 daysThe eyes open. The tipsof the first feathersappear. It performs afew movements.

EYES Nidicolous chicks areborn blind. They opentheir eyes a few daysafter birth.

INTERIOR OF THE BILLIts color is bright tostimulate the parents toregurgitate the food.

Some species have shinyareas that can be seeneven in the dark.

ShiningAreas

They lay smalleggs, with a briefincubationperiod, and theyoung arehelpless at birth.

The egg is larger, thechick is born moredeveloped, and theincubation period islonger than that ofnidicolous birds.

NIDIFUGOUS NIDICOLOUS

SIZE COMPARISON

GROWTHSTAGES

STAGES OFGROWTH

66% invertebrates.The rest consistsof seeds andflowers.

An adult bird can feed its young up to

FEATHERS The chicks areborn either nakedor with downfeathers in someareas.

MOVEMENTWithin a few hours ofhatching, nidifugousbirds can run around.

EYE They are bornwith open eyes.

66% seeds andflowers.The rest consistsof invertebrates.

24 hoursIS THE MINIMUM AMOUNT OFTIME THE BLACK-HEADED DUCKNEEDS TO BE READY TO FLY.

House SparrowPasser domesticus

Red-LeggedPartridgeAlectoris rufa

FEATHERSThe body emergesfrom the eggcovered with dampdown. Within threehours, it will becomedry and fluffy.

12-15 daysIS THE ESTIMATED TIME THAT ITTAKES THIS NIDICOLOUS CHICK TOLEAVE THE NEST.

Postnatal Development400 times a day.


A Diet for Flying

NECTARis a solution of sugar and water that flowersproduce. It is very high in energy and easy todigest. In order to get it, a bird must have along, sharp bill. In temperate regions, nectaris plentiful in the spring and summer, whereasin the tropical regions, it is available yearround. Hummingbirds and honeycreepers arevery fond of this juice.

THE HUMMINGBIRD'S TONGUELong channeled or tubulartongues suck the nectar and catchinsects at the bottom of thecorolla of a flower.

SEEDS AND GRAINSThe high energy and proteincontent of seeds make them anideal food for birds. The problemis that they are seasonal.

FRUITIn the tropics, this diet is verycommon because fruits are availablethroughout the year. In temperateand cold regions, fruit can be foundonly in the summer. Fruit has a highenergy value, and many birds eat it.

MEATHunting and scavenging birdsfeed on meat. They rarelyspecialize in one type of prey,but the prey's size determinesits selection.

LEAVES AND PLANTSFew birds feed on leaves becausethey have low energy value. Birdsthat do have undergoneadaptations that permit them todigest cellulose.

FISHThe abundance of fishthroughout the year makes themone of the favorite foods ofmarine birds. They have a highnutritional value.

INSECTIVORESInsects are rich in energy andproteins, and they are highlyabundant. Thus, many bird specieseat them. In cold regions, they canbe found only in the summer.

TOGETHER This behavior is typical ofocean birds, such as pelicansand seagulls, and of aquaticbirds, such as flamingos.When birds eat in groups,each group member can warnthe others about possibledangers, which is beneficial.

SOLITARYUsually birds of prey, such aseagles and owls, hunt alonebecause food is scarce and israndomly distributed. Huntingalone has a drawback in thatbirds must also watch out forpredators, which takes timeaway from hunting.

It is given to theyoung through thebill. Easy to digestand nutritious, it isan excellent food.

TONGUE

LAMELLAE

2.This milk has highconcentrations of thepigment that colorsthe feathers; that is why the bird'scolor changes tothe characteristicpink whilemolting inadolescence.

Most birds eat assorted foods that are rich in energyand proteins. Their high level of activity requiresthat they eat almost constantly. Their sources of

food are varied and include seeds, fruits, nectar, leaves,insects and other invertebrates, and meat of all kinds(including carrion). Many species eat more than onetype of food; some even alternate according to theseasons and to the migration cycle. This guaranteestheir survival. However, there are others birds—aminority—that consume only one type of food, forwhich they have no competition. Because theirdependence on this single source of food is greater,though, the risk is higher. Feeding behavior alsovaries among different species. For example, someeat alone, and others eat in groups.

Lamellae

Tongue

LOWERMANDIBLE

UPPERMANDIBLE

WATER IN MOTION

A second filtration occursinside the bill, as thewater is expelled. Thelamellae (small plates)catch the microorganismsbut let water and othermatter pass.

3

Hooks to Holdthe Bill

Pointed tips, in theshape of brushes

The flamingosubmerges its bill inthe briny water to feedon the microorganismsliving there.

1

The flamingo fills its billwith water by raisingits tongue. By doingthis, the flamingoperforms an initialfiltration that keeps outundesired substances.

2

The flamingo producesmilk in its crop onlywhen it is not eating. Aprotein called prolactinparticipates in itspreparation, just aswith mammals.

1.

Cross-Sectionof the Bill

Filtrationof Food

A Complex SystemFeeding on microorganisms that live in salty water demands a complex filtration system.The flamingo's bill is specially suited to this task. Its tongue and throat pump the water

inside the bill as they ascend and descend, bringing water through the hornlike lamellae, whichresemble whale baleen, to retain the food passing through them. Their tongues also have a depressedarea, where the stones and sediments that come in with the water collect. The whole operation requiresthat the flamingo submerge its bill upside down. Because of the number of microorganisms they need toconsume and the time it takes to filter them, flamingos usually spend many hours in the water. The risksinvolved in this activity are mitigated by the fact that flamingos do not eat alone, but rather in groups.Occasionally, there are instances of aggression, possibly because of territorial conflicts.

From Parents to Children

Flamingos and pigeons feed theiryoung a special “milk” that is

produced in the crop and has a nutritionalvalue similar to the milk of mammals. Bothmales and females produce it as soon asfood is ingested so that the chick is notfed regurgitated food.

3.

Strategies Depending on the abundanceof resources, the needs of the

species, and the strategies forgetting food, birds may eat alone orin groups. If food is scarce or widelyscattered throughout a region, birdseat alone and defend their territory.On the other hand, if food isabundant, they prefer to eat withinthe safe confines of the group.

Types of DietBirds expend a great deal of energy, and theirdiet must be suited to their high metabolic

rates. They eat practically anything, although the dietof some birds is very specific. The same foods arenot always available, which causes most birds toadjust their diets throughout the year.

BIRDS 57

How They Find TheirWay Around

Birds use a compass-and-triangulationsystem that lets them know where they are

according to the position of the sun or stars. Thissystem is similar to the one used by seafarers. Itconsists of measuring the sun's angle of inclinationin relation to the horizon (azimuthal angle) andcomparing it to the angle the bird knows throughits biological clock. Birds also orient themselvesby using the Earth's magnetic field. Furthermore,those migrating during the day register landmarkson their routes, such as mountains, lakes, ordeserts. Still others follow older birds or areguided by their sense of smell.

58 THE LIVES OF BIRDS BIRDS 59

BehaviorIn order to survive, millions of birdsfrom all over the world start a journey

every fall in search of better climates. Theinstinct of migrating, which other animals sharewith birds, was acquired after a longevolutionary process. Some birds fly thousands ofmiles through mountain ranges; others follow thecourse of a river without stopping until they reachtheir destination; others land after a short trip. Ingeneral, birds undergo physiological changes that arerelated to the length of their journey; some even lose almost halftheir weight during the migration. Routes tend to be fixed,although some migratory birds do not always follow them exactly.The colors on the map indicate the most important routes. There arecollective and individual migrations, and birds may travel during theday or at night. It is surprising how fast birds travel. Many studieshave recorded that carrier pigeons and white-headed sparrows cancover more than 600 miles (1,000 km) in a day. Shorebirds, such asgodwits and curlews, are among the birds that cover the mostdistance. They are also among the birds most faithful to routes.

Longitudinal

LatitudinalAltitudinalTypes of Migration

The north-south path traveled bymany species is called latitudinalmigration. A second pattern,which occurs in an east-westdirection, is called longitudinalmigration. The last pattern iscalled altitudinal migration; it isperformed by birds that move upand down mountains seasonally.

Rocky

Mountains

Amazon

Kilimanjaro

Himalayan

Mountains

Ural

Mountains

Caspian

Sea

Gulf of

Mexico

Mississippi

River

Antarctic Ocean

Peregrine FalconFalco peregrinus

White StorkCiconia ciconia

Northern WheatearOenanthe oenanthe

Curlew SandpiperCalidris ferruginea

Lesser Spotted EagleAquila pomarina

AMERIC

AN

PACIFIC

FLYW

AY

M

ISSISSIPPI FLYWAY

Wandering AlbatrossDiomedea exulans

Bar-Headed GooseAnser indicus

American Golden PloverPluvialis dominica

Bewick's SwanCygnus columbianus bewickii

Snow BuntingPlectrophenax nivalis

Barn SwallowHirundo rustica

Barn SwallowHirundo rustica

RUBY-THROATEDHUMMINGBIRDArchilochus colubris

500 miles (800 km)IS THE DISTANCE THEY FLYNONSTOP ACROSS THEGULF OF MEXICO. THEY DOIT IN JUST 20 HOURS.

ARCTIC TERNSterna paradisaea

25,000 miles (40,000 km)IS THE DISTANCE IT CAN COVER ONITS ROUND-TRIP MIGRATIONBETWEEN THE POLES. IT IS THELONGEST MIGRATION IN THE WORLD.

MEETING POINT

1 billionBIRDS MEET IN THE DEADSEA VALLEY EVERY YEARWHERE THE ASIAN,EUROPEAN, AND AFRICANMIGRATION ROUTESCONVERGE.

Siberian CraneGrus leucogeranus

Caspian TernSterna caspia

Cape GannetMorus capensis

Altai

Mountains

Great Dividing

Range

Sea

of Japan

Dead Sea

CENTRAL ASIA FLYWAY

BLACK SEA FLYWAY

EASTERN

ASIAFLYW

AY

EASTERN ATLANTIC FLYWAY

ANTARCTIC FLYWAY

WESTERN ASIA FLYWAY

Southwest

North

South

Northeast

West

Azimuthal Angle:Sun/Trajectory

Flight Direction:Northeast to Southwest

Mediterranean

Sea

Migration Routes

ATLANTIC FLYWAY

Indian

Ocean

Atlantic

OceanPacific

Ocean

N O R T HA M E R I C A

A F R I C A

A S I A

O C E A N I A

E U R O P E

Pacific

Ocean

S O U T HA M E R I C A

C E N T R A LA M E R I C A

Andes

Mountains


Defense StrategiesB irds have many predators, including cats, snakes, crocodiles, and other birds. To

defend themselves against these predators, birds use various strategies, the mostcommon of which is camouflage. Some birds blend in with their surroundings

and thus go unnoticed by their enemies. Chaparrel birds, whose plumage colors andpatterns make them difficult to discern when they are on the ground, use thisstrategy. Other birds take flight in the face of a threat. There are also thosethat keep still in the presence of unknown animals, feigning death,whereas others face an enemy and fight. It is not uncommon to seemagpies, thrushes, and other birds chasing away strangers that getclose to their nests.

BIRDS 61

Individual StrategiesAmong solitary birds, it is common toflee quickly if a stranger is present. Not

all solitary birds react this way, though; somehave developed specific techniques to defendthemselves.

ESCAPEIn the presence of terrestrial predators, a bird's firstreaction is to take flight. If the bird cannot fly, it looksfor shelter or a hiding place.

EXPANSIONOwls spread out their wings to look bigger than they really are.

DISTRACTIONLittle bustards shoot their excrement in the face ofbirds that prey on them. This distracts the predatorand makes it possible to escape.

CAMOUFLAGEis very common and is one of the most efficient defensive strategies.Many birds develop plumage to imitate the dominant colors andshapes of the environment where they live. When they notice thepresence of a potential enemy, they stay motionless to avoid callingattention to themselves. There are a few notable cases, such as thatof the tawny frogmouth (Podargus strigoides), pictured above. Manypartridges and terrestrial birds are experts at the art of blending inwith the landscape; the rock ptarmigan, for example, has whiteplumage in the winter that becomes terra-cotta in the summer.

Collective StrategiesBirds that have group behaviors usuallydevelop group strategies to protect

themselves against predators. Being numerous is aguarantee that the species will go on. They alsoadopt other tactics as a group.

COLONIESA great number of birds can defend themselves better frompredators when in groups. For that reason they even formcolonies with other bird species when raising their young.

FLOCKIn the presence of predators, birds form flocks that fly in asynchronized manner, which makes it hard for thepredators to focus on any one individual.

ATTACKS AND COLLECTIVE AIDMany birds that live in groups have developed severalhounding behaviors in the presence of potential enemies.They perform them to help an individual that is in dangeror is unable to flee.

WARNINGThey emit callings that warn the whole colony. The greatmajority of species have a specific and characteristic crythat is usually simple, brief, and very audible.They often emit these warnings while adopting postures(such as stretching the neck or shaking the wings) thatalone are enough to warn other individuals of theintruder's presence.

Defense of the BroodHatching and youth are times ofcritical vulnerability for birds. During

these phases, they are forced to keep stillbecause they are easy prey. For this reason,parents permanently watch over their nests,even attacking strangers if they get too close.

TO DEFEND ITSELF from the falcon's attack, a flock of starlings squeezes together in adense formation. If they are near a tree, they do not hesitate to hide in it.

FEIGNING INJURYA very widespread behavior is to pretend to bewounded or sick. This allows a bird to avoid beingchosen as prey. This behavior is common amongwarblers, partridges, and pigeons.

PROTECTIONWhen a parent detects danger, it gets close to itsyoung and covers them so that they are not alone.This behavior is common among tropical birds(tropical seabirds). Several species of curlews andsandpipers place their young between their legs,whereas grebes carry their chicks on their backswhen swimming.

ATTACKIn other situations, birds adopt openly aggressivebehaviors in the presence of intruders or predators.Magpies can even hound and chase away eagles if thelatter threaten their brood. Such active defenses aremore common among birds of prey.

1 2 3

FRESHWATER BIRDS 72-73

ARMED TO HUNT 74-75

TALKATIVE AND COLORFUL 76-77

THE PERCHERS CLUB 78-79

Diversity and Distribution

The environment in which anorganism usually lives is calledits habitat. In their habitats,birds find food, the best placesto build nests, and escape

routes in case of danger. An almostuniversal pattern of distribution showsthat more species live in the tropics thanelsewhere. With evolution, birds with acommon origin have diversified as they

have begun to occupy differentenvironments. This phenomenon iscalled adaptive radiation. We find oceanbirds, which have undergone manychanges in order to live near the sea, as

well as birds that live in freshwaterenvironments, in forests, and so on.Each type has acquired special physicaltraits and behaviors as a result of theadaptive process.

ONE BIRD, ONE NAME 64-65

WHERE THEY LIVE 66-67

NO FLYING ALLOWED 68-69

MARINE RESIDENTS 70-71

DUCK (Anatidae family)A natural-born fisher, ducks feed on smallsnails and aquatic insect larvae.

64 DIVERSITY AND DISTRIBUTION

One Bird, One NameT

o learn more about different birds, we give each species a name.Ancient peoples grouped birds according to practical traits andmystical beliefs. They used birds as food or considered them to be

bad omens or symbols of good luck. The people who developedscientific thought created a classification system that took intoconsideration the external form as well as the behavior of thesevertebrates; hence, the denominations predator, wading bird,and songbird were developed, among others. The most recentsystem of classification, which is based on genetic andevolutionary criteria, has generated a hierarchicalorganization of names that is constantly being updated.

ChordataAves

PHYLUM CLASS ORDER FAMILY GENUS SPECIES

Vireonidae

HirundinidaeHirundo

Hirundo rústica(barn swallow)

Vireo olivaceus(red-eyed vireo)Vireo

Larus atricilla(laughing gull)Larus

Laridae

What Is a Classification?Since the early Renaissance in the 16thcentury, scientific classifications assigned

compound names to birds, as well as to otherliving creatures. The first part stands for a genusand the second for a specific name. Thus, therock (domestic) pigeon is called Columba livia inscientific terms. The discovery of new species indifferent parts of the world widened the array ofbirds so that compound names were no longerenough. The level of family was established togroup genera of birds that share similar traits. Inturn, bird families that share common traitswere grouped into orders. These were thencombined into a category called class. Classesinclude all current and extinct birds. Birds sharea higher category in the hierarchyΩthe phylumΩwith fish, amphibians, reptiles, mammals, andvertebrates in general.

Passeriformes

Charadriiformes

HOATZINOpisthocomus hoazinis a tropical bird species that inhabits theAmazon. The presence of talons on thechicks' heels links them to their earliestancestors, including Archaeopteryx.

Diversity and the EnvironmentLiving birds are distributed among a wide variety of habitats. They can be foundin aquatic (freshwater or marine) and aero-terrestrial environments. Marine birds

live on cliffs, on islands, or in mangrove swamps. They are excellent fishers, and they useseashores or crannies between rocks as refuges for nesting. In freshwater bodies, suchas rivers and streams, ducks feed on plants and surface microorganisms. Muddy shoresare rich in insects and mollusks, which are the favorite dishes of ibis. Herons, storks, andegrets spear fish with their sharp bills as they wade in water with their long legswithout getting wet. Forests, jungles, mountain ranges, and wide plains form most ofthe world's aero-terrestrial environments. In jungles and forests, predatory birds hunttheir prey, while trogons and parrots gorge on insects and fruit. Rocky peaks are therefuge of condors, which fly for hours in search of the remains of dead animals.Ostriches run over prairies and savannas.

BIRDS 65

SPHENISCIFORMES18 SPECIESPenguins

GAVIIFORMES5 SPECIESLoons (diving birds)

PROCELLARIIFORMES110 SPECIESAlbatrosses, Petrels, and Fulmars

PODICIPEDIFORMES21 SPECIESGrebes

ANSERIFORMES150 SPECIESDucks, Geese, and Swans

PELECANIFORMES62 SPECIESPelicans, Boobies,and Cormorants

CAPRIMULGIFORMES109 SPECIESPotoos, Frogmouths,and Nightjars

APODIFORMES431 SPECIESHummingbirds and Swifts CHARADRIIFORMES

350 SPECIESSeagulls, Lapwings,and Plovers

PHOENICOPTERIFORMES1 SPECIESFlamingos

CICONIIFORMES120 SPECIESHerons, Storks,Ibises, and Egrets

GALLIFORMES274 SPECIESChickens, Turkeys, Quails,Pheasants, and Partridges

TINAMIFORMES47 SPECIESTinamous

CASUARIIFORMES4 SPECIESCassowaries and Emus

APTERYGIFORMES4 SPECIESKiwis

RHEIFORMES2 SPECIESRheas

GRUIFORMES190 SPECIESMoorhens, Cranes,and Coots STRUTHIONIFORMES

1 SPECIESOstrich

UPUPIFORMES1 SPECIESHoopoe

STRIGIFORMES174 SPECIESOwls TROGONIFORMES

39 SPECIESTrogons andQuetzals

COLUMBIFORMES317 SPECIESPigeons and Doves

CUCULIFORMES160 SPECIESCuckoos, Turacos, and Hoatzins

COLIIFORMES6 SPECIESMousebirds

FALCONIFORMES295 SPECIESCondors, Buzzards,Eagles, Vultures,and Falcons

CORACIIFORMES204 SPECIESCommon Kingfishersand Bee-Eaters

PICIFORMES382 SPECIESWoodpeckers,Toucans, andPuffbirds

PSITTACIFORMES360 SPECIESParrots, Parakeets,Lories, Cockatoos,and Macaws

PASSERIFORMES5,400 SPECIESPerching Birds andSongbirds

66 DIVERSITY AND DISTRIBUTION BIRDS 67

Where They Live

Nearctic

Afrotropic

Oceania

Indomalaya

Australasia

Neotropic

CHARACTERISTICSClimatic barrier of cold weather and oceanic isolation

Most migrating species

Many insectivorous and aquatic birds

Affinity with Palearctic

Endemic Avifauna: loons and puffins

CHARACTERISTICS

Maritime and desert isolation

Great number of Passeriformes

Many flightless birds

Endemic Avifauna: ostriches,turacos, cuckoos

CHARACTERISTICSClimatic barrier of cold weather and oceanic isolation

Low diversity of species

Most are migratory species

Many insectivorous and aquatic birds

Endemic Avifauna: wood grouse,waxwings, flycatchers, cranes

CHARACTERISTICS

Large area and number of climates

Gliders, divers, and swimmers

Abundance of fish-eating species

Many cosmopolitan species

Endemic Avifauna: albatrosses,sheathbills, petrels, penguins, and seagulls

CHARACTERISTICS

Affinities with the Afrotropical zone

Tropical birds

Many frugivores

Endemic Avifauna: ioras, pittas, swifts

CHARACTERISTICSLong isolationMany flightless and primitive birds

Endemic Avifauna: emus, kiwis,cockatoos, birds of paradise

CHARACTERISTICSLong-lasting geographicisolation

Many primitive species

Great numbers of frugivores

Endemic Avifauna: rheas,tinamous, oilbirds, hoatzins,cotingas, and stripe-backedantbirds

Species62 Families

Species73 families

Species73 families

Species15 Families

Species66 families

Species64 families

Species86 Families

This region undoubtedly has the greatest

diversity of birds. The variety in the South

American tropics, the most important

tropical zone in the world, is one and a

half times greater than that of tropical

Africa. With more than 1,700 species,

Colombia, Brazil, and Peru are the

countries with the greatest diversity of

avifauna. Even Ecuador, a much smaller

country, has more than 1,500 species.

Because of similar climatic conditions,many authors merge the Palearctic andNeoarctic regions, calling the combinedregion Holarctica.

COUNTRIES WITH THEMOST SPECIESPalearctic

Indian

Ocean

Atlantic

Ocean

Pacific

Ocean


C E N T R A LA M E R I C A


A F R I C A

A S I A

O C E A N I A

E U R O PA

With their mobility, birds have conquered all areas of the Earth. Despite thischaracteristic, there are few cosmopolitan species—that is, most birds have specifichabitats determined by climate and geographic features. Count de Buffon in the 18th

century was the first person to notice that living beings are not distributed homogeneously. Byanalyzing how animals were dispersed on the planet, he realized that different places haddifferent types of fauna. After the work of naturalist CharlesDarwin and ornithologist Philip Sclater, itbecame clear that organisms aresituated in specificbiogeographic regions.

Biodiversity in the WorldThe most diverse regions in terms of birdpopulations are the tropics because of the

favorable conditions of abundant food and warmclimate found in them. Temperate regions, however,with their seasons, are destinations for migratingbirds from tropical and polar regions. Cold regions,on the other hand, have little diversity but are rich inpopulation density. The rule is that diversity of life-forms happens in places where the environmentrequires less severe adaptations.

Adaptations According to the Environment

Birds are found in all habitats of the world, althoughmost live in tropical regions. Their ability to adapt,

however, is remarkable. From jungles to deserts, frommountains to coasts, and even on the sea, birds havesucceeded in acclimating themselves. They have undergone ahighly varied array of changes in form and behavior. Emperorpenguins not only nest in Antarctica but they also incubatetheir eggs between their feet for 62 to 66 days.The male Lichtenstein's sandgrouse hasdeveloped a sponge of feathers to bringwater to its chicks, andhummingbirds have specialwings that enable them tomake all sorts ofmaneuvers.

732

1,950

937

1,700

1,590

7 %

HOATZINOpisthocomus hoazin

OSTRICHStruthio camelus

PUFFINFratercula artica

RUBY-THROATED HUMMINGBIRDArchilochus colubris

ColombiaBrazilPeru

EcuadorIndonesia

BoliviaVenezuela

ChinaIndia

MexicoDemocratic Republic

of the CongoTanzania

KenyaArgentina

19 %

16 %

15 %

9 %More than 1,500

More than 1,000

3,37032 %

187 2 %

up to 200200 - 400400 - 600600 - 800800 - 10001000 - 12001200 - 14001400 - 16001600 - 1800

NUMBER OFSPECIES

Pacific

Ocean


5.9 ft(1.8 m)

4.6 ft(1.4 m)

1.3 ft(0.4 m)

3.9 ft(1.2 m)

RHEIFORMESRhea are common in SouthAmerican countries, such asArgentina. They look likeostriches but are smaller.Their three-toed feet allowthem to chase prey. Their longnecks and excellent eyesightmake them skillful hunters.

APTERYGIFORMESKiwis. These birds have fourtoes on each foot, and theirfeathers look like furbecause they do not havebarbules. They normally usetheir keen sense of smell tofind insects at night. Theylay only one large egg.

CASUARIIFORMESAgile runners andswimmers. The colors ontheir necks and heads aredistinctive. A bony hoofprotects them fromvegetation when they run.They have long, sharp talonson their feet.

STRUTHIONIFORMESThe ostrich is the onlyspecies in this group. It usesits wings for balance whenrunning fast. It has only twotoes on each foot. The adultmale can weigh up to 330pounds (150 kg).

The RatitesRunning birds belong tothe group of the ratites

(rata = raft, an allusion to theflat sternum). The front limbseither are atrophied or havefunctions unrelated to flying.The hind limbs have verystrong muscles as well assturdy, vigorous bones.Another difference is found inthe sternum. It is a flat bonewithout a keel, which flyingand swimming birds possess.Wild ratites can be found onlyin the Southern Hemisphere.The Tinamidae, native toCentral and South America,belong to this group(partridges).

Super SwimmersPenguins' bodies are covered with three layers of small, overlapping feathers. A penguinhas small limbs and a hydrodynamic shape that helps it swim with agility and speed.

Dense, waterproof plumage and a layer of fat insulate the bird from the low temperatures ofthe regions where it lives. Since its bones are rigid and compact, it is able to submerge itselfeasily. This adaptation distinguishes it from flying birds, whose bones are light and hollow.

PENGUIN HEADING TO THE WATER

Other WalkersMore than 260 species belong to the order Galliformes, whichincludes chickens, turkeys, and pheasants. The birds in this

group have keels, and they perform abrupt and fast flights, but onlyin extreme situations. Their feet are suitable for walking, running,and scratching the ground. This group includes the birds that humanbeings use the most. In general, males are in charge of incubatingand raising the young.

BIRDS 69

No Flying AllowedA

few birds have lost their ability to fly. Their maincharacteristic is wing loss or reduction, although for somea remarkable size may be the cause of their inability to fly.

Such birds weigh more than 39 pounds (18 kg). This is thecase with runners (ostriches, cassowaries, emus, rheas,kiwis), extremely fast birds that live in remoteareas of New Zealand, and swimmers, such aspenguins, that have developed extraordinaryaquatic abilities.

Running and Kicking Ostriches usually run to escape from predatorsor to hunt small lizards and rodents. In both

cases, because of their strong legs, they are able toreach a speed of 45 miles per hour (72 km/h) and tomaintain it for 20 minutes. When running is notenough to protect the bird, kicking is a valid recoursethat discourages the attacker. In courtship displays,forceful stamping is also used to win over females.

FLATSTERNUM

ATROPHIEDWINGS

LONGNECK

SMALLHEAD

PELVIS

GREATER DIVERSITYIn many cases, running birds can be found inmany parts of the world because of humanintervention. The area where flightless birdshave diversified the most is Oceania, due tocontinental isolation.

Clumsy andflapping fast2

FLYING WITH LITTLE GRACE

OCEANIA

ASIA

NewZealand

Taking a runand jump1

Emergencylanding3

KEEL-SHAPEDSTERNUM

ON TWO TOESWith just two toes, thecontact surface betweenthe foot and the groundis relatively small. This isan advantage whenmoving on land.

TARSUSMETATARSUS

PHALANGES

PLANTAR CUSHION

PHALANGEAL CUSHION

TOE

CLAW

VERTEBRAETHE NUMBER ANOSTRICH HAS INITS NECK

18

2 ft(0.6 m)

HUNTINGThe wings work likeflippers. The foot—withfour joined toes pointingbackward—and the tailsteer the direction ofthe dive.

BREATHINGWhen looking for food,penguins need to leave thewater and take a breathbetween plunges.

RELAXINGWhen resting in thewater, they move slowly.They float on the surfacewith their heads up andbalance their bodies withtheir wings and feet.

Runner's ChestThe keel-shaped sternumof flying and swimmingbirds offers a largersurface for attachment ofthe pectoral muscles. Theflat sternum of runningbirds has a smallersurface and,consequently,less mobility.

AFRICAN OSTRICHA single species inhabitseastern and southern Africa.Adults reach a height of 9feet (2.75 m) and a weight of330 pounds (150 kg).

ROBUSTBONE

SHORTFEATHERS

ELBOW

HANDBONES

WRIST FLIPPERSThe short, compact wings looklike flippers. They are essentialto the penguin's underwatermovements.

Rockhopper Penguin Eudyptes crestatus


Marine ResidentsO f the more than 10,000 bird species inhabiting the Earth, only about 300 have managed to

adapt to marine life. To survive at sea, they have undergone multiple adaptations. Forinstance, marine birds have a more efficient excretory system than that of other species,

including a specific gland that helps them eliminate excess salt. Most marine birds live on thecoasts and have mixed behaviors; others are more aquatic than aerial. A few—such as albatrosses,petrels, and shearwaters—can fly for months at a time, landing only to raise their chicks. They arecalled pelagic birds.

CentralExcretory Canal

BloodCirculation

Circulation ofSaline Solution

Membrane

Toe

FourthToe

TUBULAR NOSTRILSAlbatrosses have one oneach side of their bills.On petrels andshearwaters, the tubularnostrils have merged ontop of the bill, forming asingle nasal tube.

AdaptationsMarine birds are well prepared to liveon water, especially those that fish out

at sea. The tips of their bills are hook-shaped,and their feet have webbed membranesbetween the toes. They also have anadmirable ability to float. The saline water is

not a problem; these birds can even drink it.In some pelagic birds, sense of smell plays animportant role in enabling them to detect theoil of the fish in the water to find schools offish. They also use their sense of smell to findtheir nests in colonies.

Fishing MethodsMany marine birds fish by diving intothe sea. This way, they can access fish

that swim below the surface. In order toreach deeper levels in the water, they fly upseveral feet, spy a school, fold theirwings, and plunge with their necksstretched forward. Thanks to thebuoyancy of their feathers, they areback on the surface moments later.

HERRING GULLLarus argentatusA voracious fisher andgreat glider. There aremany species, some trulycosmopolitan.

IMPERIAL SHAGPhalocrocorax atricepsThis great coastal diverhas solid bones and strongswimming feet. It does notoil its plumage so that itcan better submerge.

BROWN PELICANPelecanus occidentalisIt stays on the shore. Ituses its crop as a fishingnet while it swims.

VARIOUS MARINE BIRDS

148 feet (45 m)IS THE MAXIMUM DEPTH THEY REACH. COMMONLOONS—BIRDS INDIGENOUS TO NORTH AMERICATHAT SPEND THE WINTER AT SEA—HAVE BEENRECORDED TO REACH THIS DEPTH. ALMOSTUNABLE TO WALK, COMMON LOONS AREEXCELLENT SWIMMERS AND DIVERS. THEY NESTAT INLAND LAKES DURING THE SUMMER.

DIVEFISHING

The birddives togain speed.

It folds its wings andstretches out its neckto immerse itself inthe water and reachthe school of fish.`

The bird immerses its bodyas much as possible tocatch the fish; its featherscause it to float back up.

1.

2.

3.

CAPE GANNETMorus capensisSkillful spearfishers. Theylive in colonies in Africa. Tohelp cool themselves, theyhave a strip of naked skinon their throats.

Salt GlandLiving in the ocean requires a few adaptations.The most notable one is the salt gland, which

eliminates excess salt from the bloodstream. This way,marine birds can even drink salt water withoutsuffering dehydration, as would be the case withhumans. This gland is very efficient: it has beenobserved that 20 to 30 minutes after drinking a salinesolution with concentrations similar to that of theocean (4 percent), birds eliminate another solution(through the nostrils) with 5 percent salt, in the shapeof water drops.

Lobe

GlandHOOK-SHAPED TIPPrevents thefish fromsliding andfalling away,once caught BILL

It is composedof several hardplates.

COMMON LOONGavia immer

CORMORANTBILL

TOTIPALMATE FEETA characteristic of many marine birds. Theposterior toe (hallux) is joined to the other toesby a membrane. It creates more surface area, andtherefore more push, as the bird swims. Birdswith this kind of foot walk clumsily.


Freshwater BirdsT

his group includes birds that vary greatly—from commonkingfishers to ducks to storks—and covers a wide spectrum.Freshwater birds live in rivers, lakes, and ponds for at least part of

the year and are perfectly adapted to aquatic life. Some are excellentswimmers, whereas others are great divers. An important group wadesin watercourses with long legs as they fish. Freshwater birds have avaried diet and are mostly omnivorous.

Ducks and DistantCousins

The order Anseriformes includes birdsthat are very familiar to humans:

ducks, geese, and swans, for example. Theyhave short, webbed feet and wide, flat billslined with lamellae (false teeth) that enablethem to filter their food, catch fish, andscrape the beds of rivers and ponds. Mostare omnivorous and aquatic (either stayingon the surface or diving), although somespecies spend more time on land. They arewidely distributed, and the plumage ofmales becomes very colorful during thecourtship season.

It swims on the surface,looking for foodunderneath the water.

1 It sticks its head into thewater, abruptly pushesback its feet, and turns itsneck downward.

2 It floats face-downand pokes the bottomwith its bill.

3

IBIS (Ibis sp.): Some filtrate,and others fish.

STORK (Ciconia sp.): Itfishes with its long bill.

Shovel-Shaped Bill:Typical of many ducks.The size varies.

Mandarin Duck Bill:One of the smallest-billedspecies.

SHOEBILL (Balae-niceps rex):It eats among floating sedges.

HERON (Egretta sp.): Itfishes with its sharp bill.

COMMON SPOONBILL(Platalea leucorodia): It eatsseveral types of aquatic animals.

HAMMERKOP (Scopusumbretta): It fishes andhunts small animals.

Muscovy DuckCairina moschata

White-Fronted GooseAnser albifrons

Black-Necked SwanCygnus melancoryphus

Wading Birds These birds belong to an artificial ordersince, from a genetic perspective, the

species are not related. They are groupedtogether because adaptation to the same habitathas caused them to develop similar shapes: longbills and necks to perform skillful movements andthin legs designed to wade across the water asthey fish. Herons form a special group because they arecosmopolitan and because they have powder down feathers.Ibis and storks also have a wide distribution (area in whichthey occur). Birds that have spoon- and hammer-shaped billsare found primarily in Africa.

26 to 34inches (66–86cm)



GREBEPodiceps sp.

STONE CURLEWBurhinus oedicnemus

12 to 16in (30–40 cm)

A DUCK'S DIET

Divers and Other FishersDiving birds belong to the family Podicipediformes. They feedon small fish and aquatic insects. They are very clumsy on

the ground. In the Coraciiformes order, common kingfishers andother similar birds find their prey by closely watching the water.When one of these birds notices a small fish, it spears it, catchingit with its bill. In the order Charadriiformes, curlews wanderaround the edges of ponds in search of food. Their long legs keeptheir bodies out of the water. They are not swimmers.

THE BILL OF AN IBISis long and thin, ideal tostick in the mud to lookfor food.

THE LEGS OF AN IBISkeep the bird above thewater but close enough tofish. Ibis also stir up thebeds of lakes and ponds.

UnfoldedWeb

FoldedWeb

COMMONKINGFISHER(also known asEuropeanKingfisher)Alcedo attlis

DUCK BILLSare flat, wide, and slightly depressed toward the middle. Ingeneral, their shape does not vary, but there are species withtiny bills (the mandarin duck, for example).

ORIFICESOpen and oval

LAMELLAEAround the insideedges of the bill

HOW THEY USE THEIR FEET TO SWIMA duck moves its feet in two ways. To advance, it spreads out its toes anduses its webbed feet to row. It closes the toes to bring the foot forwardagain. If the bird wants to turn, only one foot pushes to the side.

1 in(2.7 cm)

2 to 4 in(5–10 cm)

FulvousWhistling Duck

Dendrocygnabicolor

White IbisEdocimus albus

16 in(40 cm)

7 in (18 cm)

BIRDS 7574 DIVERSITY AND DISTRIBUTION

Armed to HuntB

irds of prey are hunters and are carnivorous by nature.They are perfectly equipped to eat living animals. Theireyesight is three times sharper than that of human beings; their

ears are designed to determine the precise status of their prey; theyhave strong, sharp talons; and they can kill a small mammal with thepressure of their talons alone. Their hook-shaped bills can kill prey bytearing its neck with a single peck. Eagles, falcons, vultures, and owlsare examples of birds of prey. Birds of prey can be diurnal or nocturnal,and they are always on the lookout.

BALD EAGLEIts hook-shaped bill iscommon to many birdsof prey.

FALCONIt can break the spineof its prey with itsupper bill.

SPARROW HAWKIts thin bill enables it totake snails out of theirshells.

GOSHAWKIts strong bill can catchprey as large as hares.

5 miles(8 km)IS THE DISTANCE FROMWHICH A FALCON CANPERCEIVE A PIGEON.

Diurnal and NocturnalEagles, falcons, and vultures arediurnal birds of prey, whereas owls

are nocturnal—that is, they are activeduring the night. These two groups are notclosely related. These birds' main preyincludes small mammals, reptiles, andinsects. Once they locate the victim, theyglide toward it. Nocturnal birds of prey arespecially adapted: their eyesight is highlydeveloped, their eyes are oriented forward,and their hearing is sharp. The feathers ontheir wings are arranged in such a way thatthey make no noise when the bird is flying.In order to protect themselves whilesleeping during the day, they have dullplumage, which helps them blend in withtheir surroundings.

HOW THE VULTURE HUNTS

BillsThe bills of birds of prey are hook-shaped. Some birds of prey have a

tooth that works like a knife, allowingthem to kill their prey, tear its skin andmuscle tissues, and get to the food easily.The structure and shape of the bills of birdsof prey changes depending on the species.Scavengers (for example, vultures and condors)have weaker bills because the tissues ofanimals in decomposition are softer. Otherspecies, such as falcons, catch prey with theirtalons and use their bills to finish it off with aviolent stab to the neck, breaking its spine.

TIPWhere thetooth islocated

NOSTRILOlfactorycanals

Most birds of prey catch and kill their prey with theirtalons and tear away the meat with their bills. For this

reason, birds' feet constitute one of the morphologicalcharacteristics of a species. The toes end in strong, sharp nails

that the bird uses as pincers to catch itsprey in flight. The osprey also has thorns on thesoles of its feet, which help it to catch fish.

Feet

BALD EAGLEHaliaeetus leucocephalusIt has a visual field of 220degrees and a bifocal visionof 50 degrees.

DIMENSIONSThe wings of birds of prey areadapted to suit their flyingrequirements. They can measureup to 10 feet (3 m).

Condors 3 to 9.5 ft (0.95–2.9 m)

Eagles 4.5 to 8 ft (1.35–2.45 m)

Buzzards 4 to 5 ft (1.2–1.5 m)

Kites 2.6 to 6.4 ft (0.8–1.95 m)

Red-Backed Hawk3.4 to 4.4 ft (1.05–1.35 m)

Falcons 2.2 to 4.1 ft (0.67–1.25 m)

1Vultures feedmainly on carrion,although they areable to attack aliving animal if itis vulnerable andthe situationpresents itself.

Thanks to theirability to glideon thermals,vultures can findcarcasses onwhich to feedwithout wastingenergy.

Once they find food, theymust analyzethe territory toknow if theywill be able totake flightagain soon.

2 3

EURASIAN EAGLE OWLBubo buboIts ears are asymmetrical andcan determine the location ofprey with great precision.

CEREFleshy formation,somewhat thickand soft

Zone-Tailed HawkButeo albonotatus

OWL PELLETSOwls produce pellets. Theyswallow their prey wholeand regurgitate theindigestible substances.The study of pellets makesit possible to determinethe fauna of small areaswith great precision.

GRIFFON VULTUREIts long toes do not havea good grasp.

FISHING EAGLE Its toes have rough scales that looklike thorns, which help it to catch fish.

GOSHAWKIt has calluses at the tips ofits toes.

SPARROW HAWKIts feet have tarsi and short,strong toes.

BIRDS 7776 DIVERSITY AND DISTRIBUTION

Talkative and Colorful

Eating, Climbing,and Chattering

Parrots use their bills to feed and tomove about tree branches; they use

their bills as an extension of their feet to givethem support when they climb. Parrots alsohave a curved profile, a pointed tip on theirupper mandible, and sharp edges on theirlower one. These adaptations are practicalwhen it comes to cutting and breaking fruitsand seeds. The largest species like fruits withshells, such as walnuts, hazelnuts, andpeanuts. The smaller ones prefer nectar andpollen, which they obtain with the help ofbrush-shaped bristles on their tongues. Theirability to imitate the human voice has madethem very popular. However, they are farfrom being able to produce language. Inreality, they are merely good imitators: theyuse their excellent memory to imitate sounds.They do this when they are hungry or whenthey detect the presence of unknown people.

UPPER AND LOWER MANDIBLESThe hook-shaped bill is flexible; the mandibles arejoined to the skull by hinges. At its base, the uppermandible has a fleshy protuberance called a cere.

NOSTRILSThey are located atthe base of the bill'supper portion.

UPPER PART OFTHE BILLIt is where the mostpressure is exertedand fruits are tornopen.

HOOKED BILL

HOOKSharp projectionused to open seeds

The Feetare referred to as zygodactyl. This meansthat two toes project forward and two

project backward. Parrots appear to strutbecause their feet have a tibiotarsus that isshorter than that of other birds.

FEATHERS AND COLORSThey have tough and lustrous plumage. Anabundance of green feathers helps them tohide among the leaves. In South America,the array of colors includes hues of blue,yellow, and red.

Parrots form a very attractive bird group with a great capacity for learning. This groupcomprises cockatoos, macaws, and parakeets. They share physical characteristics, such as abig head, a short neck, a strong hook-shaped bill, and climbing feet. They have plumage in

many colors. Toucans and woodpeckers share with parrots the colors of their feathers and theirtype of feet. Toucans have a wider, thicker bill, but it is light. Woodpeckers are climbing birds witha strong, straight bill, a tail of stiff feathers, and a distinctive crest. They form numerous groups,and most nest in trees.

COMPARISONAmerican parrots vary in size,from the monk parakeet(Myopsitta monachus), whichis 12 inches (30 cm) tall, to thehyacinth macaw(Anodorhynchus hyacinthinus)from South America, which is33 inches (1 m) tall.

WINGSUsually they areshort and rounded,suitable for flyingamong branches.

FEET LIKE HANDSIn some species, the left foot is longer.They use it to grab fruits and tear themwith their bills.

MONK PARAKEETArgentina12–14 in (30–35 cm)

0 in or cm

20 in (50 cm)

39 in (100 cm)

HYACINTHMACAWBrazil/Bolivia39 in (100 cm)

COCKATOOMexico16–20 in(40–50 cm)

B.A.

THE HABITAT OFWOODPECKERS

They live in the woods andcan often be heard

there. Theiradaptations to

arboreal life aredemonstrated by their strong,

thick bills and their stiff tails, whichthey use for support, together with

their feet. They use their hearing tolocate tree-boring insects; they thenpeck the wood incessantly until theyfind them.

QUETZALSThey belong to the family

Trogonidae. They have feetadapted to arboreal life.

Males have brilliantplumage and long,

attractive tails.

TOUCANS Their big bills haveserrated edges thatsuit their diet of fruit.They live in the SouthAmerican jungles.

WOODPECKERShollow out tree trunks with pecks inorder to build a nest and to feed oninsects that eat wood.

Family AlbumFour basic groups have been established to facilitatethe study of families: passerines with wide bills;

ovenbirds, whose plumage is dull and brown (ovenbirds arenoted for the great care they take in building nests);lyrebirds, whose tails have two external feathers that arelonger than the others; and songbirds, with their elaborateand pleasant singing. Songbirds form the most numerous andvaried group; it includes swallows, goldfinches, canaries,vireos, and ravens.

PERCHING FOOTThree toes projectforward, and the well-developed halluxprojects backward.This type of footallows the bird to holdon tightly to branches.

HARD, SHORTBILLThe bill of a swallowis very short andtough. The swallowcan use it to catchinsects in flight.

SINGER

This blue-and-whiteswallow (Notiochelidoncyanoleuca) intones itspleasant and trillingchant while it flies orwhen it alights. Larks,goldfinches, canaries,and other passerinesdelight us with theirtrills and sounds.


SYRINXThis sound-producingorgan is located atthe end of thetrachea. The musclesin the syrinx movethe bronchial walls,which, as the airpasses through,produce the melodicsounds thatcharacterizesongbirds.

BIRDS 79

The Perchers ClubP

asserines—or Passeriformes, the scientific name—form the widest and most diverse order of birds.What distinguishes them? Their feet are suited for perching and, therefore, for living among trees,although they can also stroll on the ground and through the brush. They inhabit terrestrial

environments all over the world, from deserts to groves. Their complex sounds and songs originate from avery well-developed syrinx. Their chicks are nidicolous—that is, naked and blind at birth. In their youth,they are agile and vivacious, with very attractive, abundant, and colorful plumage.

Passerines are small in comparison with other birds. Their sizevaries from 2 inches (5 cm) (bee hummingbirds, Mellisugahelenae) to 7 inches (19 cm) (Chilean swallow, Tachycinetaleucopyga) to 26 inches (65 cm) (common raven, Corvus corax).

THE SMALLEST

HUMMINGBIRDS 2 in (5 cm)They get so much energy fromnectar that they can doubletheir body weight by eating.However, they use this energyup during their frantic flights.

LIVING AT THE EXTREMESThey range from one hemisphere to theother. They raise their chicks in thenorth and fly to the south to spendwinter there. They fly all the way toTierra del Fuego. Their sense ofdirection is remarkable. They can findand reuse their nests after returningfrom a migration.

RAVENS 26 in (65 cm)They eat everything:fruits, insects, reptiles,small mammals, and birds.They are skillful robbers ofall kinds of food.

50%THE PERCENTAGEOF BIRDS THATARE INCLUDED INTHE ORDERPASSERIFORMES

A

B

Passerines have been classified into79 families, with more than 5,400different species.

PASSERIFORMES BIRDS

SyringealCartilage

TrachealRing

BronchialMuscles

BronchialRing

OVENBIRDS ANDTHEIR RELATIVES

Their nests arecompletely coveredstructures, similar toovens. Other members ofthis family build nestswith leaves and straw,weaving interestingbaskets. Still others digtunnels in the ground.

WIDE BILLS

They are native to Africaand Asia and inhabit tropicalzones with dense vegetation.They eat insects and fruits.They produce nonvocalsounds with the flapping oftheir wings. They do thisduring courtship, and thesound can be heard 200 feet(60 m) away.

LYREBIRDS

There are only two speciesof these Passeriformes,and they are found only inAustralia. They are verymelodic and are excellentimitators of other birds.They can even imitate thesound of inanimate objects,such as horses' hooves.

In the summer, during thereproductive season, they

live in the Northern Hemisphereon the American continent. Ingeneral, neotropical migratorybirds are those that reproduceabove the Tropic of Cancer.

A

When winter arrives in theNorthern Hemisphere, they

perform a mass migration to thesouth, occupying the Caribbeanand South America. The barnswallow travels 14,000 miles(22,000 km) during itsmigratory trip from the UnitedStates to southern Argentina.

B

BARN SWALLOW (Hirundo rustica) Barn swallows spend mostof their time traveling totemperate zones.

SWALLOWS 7 in (19 cm)Swallows have greatagility and skill. Thesepopular migratory birdshave bodies suited forlong trips.

BIRD DOMESTICATORS 88-89

ENDANGERED SPECIES 90-91Humans and Birds

Human beings have long takenan interest in studying thesehigh-flying creatures. Theyhave served as a source offood and have sometimes been

used as indicators of the arrival of rain,storms, or the presence of commonenemies, such as dangerous reptiles.Evidence of ancient peoples' venerationof birds can be found in documents,

paintings, and reliefs. The Egyptianswere the first to domesticate pigeons.Today several species brighten uphomes with their colors and cooing.Other types of birds, such as sparrows

and swallows, live with us in cities. Thedestruction of bird habitats, through theexcessive exploitation of naturalresources, is one of the main causes ofbird extinctions.

BIRDS AND HUMAN CULTURE 82-83

HOW TO GET TO KNOW BIRDS 84-85

AMONG US 86-87

ROBIN CHICKS (Erithacus rubecula)Although their natural habitats arehumid groves, they usually seekshelter in cities, always close to water.

82 HUMANS AND BIRDS

Birds and Human CultureB

irds fly, sing, dance, and have showy plumage. Because of these qualities,they have fascinated human beings throughout history. Some species, suchas eagles, have played an important role in world literature because of

their aggressiveness and beauty. Some birds have also been assigned symbolicmeanings: doves, which currently represent peace, are one example. Humanbeings have also been able to make use of birds. In the past, they were oftenused by sailors to find land, and in other cases they were trained to hunt.

FENGHUANGwas the messenger bird ofXi Wangmu, goddess offertility and eternity inancient China. A detail of apainting in the caves ofMogao, Dunhuang, China,is pictured above.

QUETZALPictured above is a detail of aMayan ceramic piece featuringquetzals, Mesoamerican birdswith long green tails, from which,according to myth, the godQuetzalcóatl took his clothing andname: “feathered serpent.”

HORUS, THE FALCON, is an important god inEgyptian mythology. His eyes represent the sunand the moon, and together with Seth hewatches over the boat of Ra, which carries thedead away on the Nile.

Bird SymbolismThroughout history and across cultures, humanbeings have used birds to symbolize several

concepts. The fascination that their flight creates was asource of inspiration for such interpretations. Today thestrongest and most widespread association is that of theflight of birds with freedom. In distant times (and in not sodistant times), however, birds have represented many otherthings, from fertility and happiness, with their spring songs,to deep mourning, in the case of crows and vultures.Wisdom has been associated with owls, and shrewdnesswith crows. According to a certain modern tale, storks areresponsible for bringing babies, and eggs are the universalsymbol of gestation.

Dressing Up in FeathersAlmost all cultures have used bird feathersfor decorative and ritualistic purposes. Their use

as ornaments extended to North and South America,Africa, and the Western Pacific. North Americanindigenous peoples featured them on their waroutfits, Hawaian kings wore them on their royalcostumes, and the Mayans and Aztecs used themin works of art.

Rites and BeliefsBirds have long enjoyed a prominent place in religion—first as totems and then asiconic representations of gods. Many religions have featured deities with the wings or

heads of birds. Birds were also celestial messengers, and the future was interpreted throughtheir flights. The crow was Apollo's messenger in ancient Greece; the Maya and Aztecs hadQuetzalcóatl, their supreme god, who was named after the quetzal (a brightly colored CentralAmerican bird); and the Egyptians represented their fundamental god Horus with a falcon.

FalconryThis practice originated inAsia, in the homeland of the

nomadic Mongols—descendants ofGenghis Khan—where, to this day, it is commonlyused as a form of subsistence by part of thepopulation. It consists of using birds of prey(mainly falcons) to hunt. Trained birds aretypically carried, hooded, and perched ontheir masters' arms. When released, theyfly at high altitudes looking for prey, andthen dive toward the ground to hunt it.They carry the prey back to theirmasters, who reward them with food.The basic training process takes alittle over a month and a half.

COMPETITOR BIRDSWhen birds share a habitatwith humans, they oftencompete for resources (light,water, space, and nutrients).This is the case with birdsthat feed on cultivatedcrops. Urban areas, whichhave buildings that offergood nesting sites, attractmany birds. This fact can becommonly observed insquares and open spaces,where pigeons and sparrowsform veritable flocks.

GLOVE

TRANSMITTER

FALCON

LASH

STRAPS

HOOD

NORTH AMERICANINDIGENOUS MANwearing a warcostume coveredwith feathers

PIGEON Sometimestheir numbers inurban areas becomeexcessive.

DOVEDoves currently stand for peace, butin ancient Greece, Syria, andPhoenicia, they were used as oracles.In Mesopotamia and Babylon, theyembodied fertility. For Christians,they symbolize the Holy Spirit andthe Virgin Mary.

EAGLEIn Greek mythology, it was thesymbol of Zeus. The Romans usedit on their legions' banners. Formany native North Americancultures, it represented war, and itwas the emblem of feudal lordsand emperors. Today it is thenational symbol of Mexico and theUnited States.

SPARROW Thesparrow is one of thebirds best adapted tothe urban environment.

ELEMENTSBirds and masters wear specific clothes.In addition to gloves, hoods, and straps,radio transmitters are now also used tolocate the birds as they fly.

GARUDA FRESCOPictured above is a winged deity, featured on afragment of a mural fromthe Hindu temple ofGaruda, in AnantaSamarkhom,Bangkok, Thailand.`

84 HUMANS AND BIRDS

How to Get to Know BirdsO rnithology (from the Greek ornitho, “bird,” and logos, “science”) is a

branch of zoology that studies birds. Ornithologists and a great numberof bird lovers, who enthusiastically want to know more about these

creatures, carry out the task methodically and patiently. They observe,analyze, and register birds' sounds, colors, movements, and behavior intheir natural environments. To undertake this fieldwork, they developmethods and techniques and usetechnological resources to trackspecimens and learn about whathappens to them during giventimes of the year.

NASAL MARKERSThese are colored, numbered plasticdisks placed on the bill. They arefastened to the nasal orifices ofaquatic birds.

NECK MARKERSWhen placed appropriately,necklaces are effective markerswith few adverse effects ongeese, swans, or other aquaticbirds with long necks.

CAMERA WITHZOOM LENSA camera with apowerful lensprovides the

opportunity torecord details that simplecameras cannot.

BINOCULARSThey make it possibleto see details in colorand shape withoutdisturbing the birds.Their usefulnessdepends on the powerof their lenses.

STUDIESMany studies onanatomy, physiology,and genetics ofdifferent bird speciesare carried out inlaboratories.

WORK CLOTHESAlthough seemingly asmall detail, clothes canbe a hindrance. Theyshould be comfortableand soft, appropriatefor the weather, andof colors thatblend into theenvironment.

TAPE RECORDERRecording birds' noisesand songs makes itpossible to distinguishamong birds. Expertscan identify species bylistening to theirrecordings.

BIRDS 85

Direct ObservationObserving in a bird's natural habitat provides muchinformation. For the greatest success, bird-watchers

typically place themselves in front of rocks or trees inorder not to form a silhouette. An alternative technique isto create a hiding place, such as a hollow cardboard rock.In both cases, the watcher needs to be facing away fromthe sun and must be prepared to stay for a long time.

Catching Birds

The Marking of Captured Birds

This technique provides data onmigration, survival, and

reproduction rates, among other data.The bird should not suffer adverseeffects in its behavior, longevity, orsocial interactions. Under nocircumstances should thisprocedure hurt a bird. To avoidhurting birds, rings aredesigned to be placed onthem rapidly and easily, yetto stay in place until theresearch is completed.

MIST NETThese fine nets are usuallyplaced over swamps ormarshes, and they cancatch small birds. Once thebirds are identified with aring or some other tag,they are set free.

HELIGOLAND TRAPIt consists of a large barbed-wire funnel or corridor thatends in a box. Birds caughtlike this are tagged so thatthey can be monitored andstudied later on.

PAINTS AND DYES Birds that visit environments with densevegetation are normally marked with nontoxiccolorings on the feathers of their highest andmost visible body parts.

Scientists take advantage of molting to studypenguins. When they are changing

plumage, these birds stand on theirlegs, which makes it difficult to

place or observe any rings ontheir legs. Instead, strips are

placed around their wings, orelectronic chips are

implanted in their skin. Thelatter technique is less

harmful because it doesnot potentially hinderthe animal.

CANNON NETSThese nets are “shot” overbirds using cannons orrockets. They unroll andcatch birds as they areeating or resting. They areused to catch large birds.

RINGEDNumbered aluminum ringsare used. When placing oneon a bird, one should makesure that it slides and turnsaround the tibiotarsus to avoidhurting the bird or causing itto change its activity.

WING MARKERSThey are very visible and can be codified for individualidentification. They stay on the bird for long periods of time andare normally used on birds of prey.

Among Us

86 HUMANS AND BIRDS

The urban environment presents opportunities for birds. It offers advantages in finding food andshelter. People, young and old, give bread crumbs to these interested visitors. When birds cometo cities, houses and parks offer them protection. They can find more options when it comes to

building a nest. Seagulls and owls have changed their behavior by adapting to the city, and otherspecies, such as some sparrows, are no longer able to survive without a human presence. However, noteverything is an advantage. In the city, birds have to face dangers and obstacles that do not exist intheir natural habitat: a utility wire or a car can be fatal.

BIRDS 87

Where to Find ThemIn big cities, groups of birds can be found in different areas. Busy andnoisy areas, such as squares, parks, and gardens, attract many species.

Calm, deserted spaces, such as cemeteries or deserted buildings, are chosen bybirds in search of peace. Other places where birds choose to eat and sleep includeplots and landfills with lots of food, as well as nooks in high places, such asbalconies, belfries, and roosts.

PLOTS AND CEMETERIESPlants with seeds usually grow in these places,which are located far from urban centers. Forthis reason, magpies and nightingales favor them.

URBAN CENTERS With the arrival of cold weather, different bird species from thecountryside and the mountains come to the city. In general, theystay until the beginning of spring. In the winter, more birds, such aschiffchaffs, great tits, and robins, can be observed in cities.

PARKS AND GARDENSRoyal peacocks and green peafowls share theseplaces, where they can find the microhabitats ofinsects on which they feed. Parks and gardens mayhave ponds that are visited by other bird species aswell. Few species nest in these places because thesespaces offer little quiet.

GROVE

DAY/NIGHTArtificial night lightingintensifies birds' activities.They organize their tasksaccording to street lighting.

BLACKBIRDSwere originallymigratory, but asthey adjusted tocities, they becamenonmigratory.

SEAGULLSusually fight amongthemselves for the foodthey get from landfills.

WAGTAILSnest in holes or crannies,always near water.

Population ControlWithout enough predators and with anabundance of food, urban bird

populations grow exponentially.

The Urban EnvironmentThis setting is characterized by environmental andclimatic factors that are different from the natural

ones. It has more varieties of plants, higher averagetemperatures, less wind, more rain, cloudier skies, and lesssolar radiation. Polluted air and soil are harmful factors forboth humans and birds.

TEMPERATUREINCREASEDOWNTOWN

1.5ºWINDINTENSITYDECREASE

15%RAININCREASE

10%

ROBINSThey get close onlyto find food. Theirtrills and plumageare attractive.

DIETSome species, which areveritable strategists, benefitfrom human activities. Forexample, seagulls can feed ongarbage; great tits drink milkfrom containers by adroitlyuncapping them; and somemagpies have learned to tearcardboard containers to eatthe eggs inside.

PIGEONSspend a lot of timetogether. They aregranivores but eat allkinds of food.

SWIFTSare insectivores.They catch theirprey in flight.

FALCONSDiurnal birds of prey.They nest on the roofsof high buildings.

RAVENS, CROWS, ANDRELATED BIRDSLIVE IN MOSCOW.

800,000

PIGEONS DESCEND ON THE SQUARESAND STREETS OF BARCELONA.

160,000OWLSBelfries or abandonedbuildings are the homes ordormitories of these birds.

FEEDERWITHFRUITS

STORKSbuild their nestson rooftops.

LANDFILL

ABANDONEDBUILDING

SPARROWSSmall birds with ahighly varied diet

88 HUMANS AND BIRDS BIRDS 89

Bird Domesticators Farm ModelWhen compared to other farm animals,birds grow and reproduce easily. They

need to have a place with appropriatetemperature, humidity, and ventilation in orderto yield the desired amount of meat or eggs.For this reason, it is necessary to maintaincontinuous environmental and sanitary controlof the area in which they are bred. Ideally theyshould be able to walk, run, scratch the earth insearch of food, and take sunbaths. Additionally,to protect them from predators and frominclement weather, it is important to shelterthem in coops. This allows them to restpeacefully and sleep at night.

AIRMAILFor more than 1,700 years, humanbeings have used pigeons to sendmessages. Armies have used themas communication aids duringwars. Pigeon keeping is thepractice of breeding and preparingpigeons to become messengers, atask that makes the most of theiragility and intelligence.

BIRD FLU

TURKEYOn the American continent,these birds were domesticatedby the indigenous pre-Columbians from a wildMexican species calledMeleagris gallopavo gallopavo.

GOOSEContemporary domesticbreeds descend from wildAsian and easternEuropean species. They arevoracious, which makesfattening them easy.

DUCKThese birds are animportant source offood in Southeast Asia.In Central and SouthAmerica, theconsumption of ducks isless widespread.

The domestication of birds is a very old activity, as shown by records fromdifferent cultures in different parts of the world. It was related to theadoption of a sedentary way of life by human populations.

DOMESTICATION IN HISTORY

MIXED DIETBirds look for insects andplant shoots as they peckthe soil. The breedercomplements this dietwith nutritionallybalanced foods.

QUENCHING THIRSTTen chickens drinkfrom 0.5 to 0.8 gallon(2–3 l) of water a day.The farmer providesthem with water introughs, which areplaced all over thehenhouse.

5000 BC

IndiaThere are recordsof domestic geesein India, beginningin 5000 BC.

2000 BC

Far EastDescendants of the royalduck (Anas platyrhynchos)were domesticated in thisarea of the Asian continent(what is now China).

1492

MexicoThe Spanish colonizersencountered turkeysdomesticated byinhabitants of theNew World.

2The virus can betransmitted to themost common ofdomestic birds:chickens.

1 Ducks carry theH5N1 virus butare immune tothis disease.

The H5N1 virus istransmitted tohumans throughdirect contact withdomestic birds.

3

At Your ServiceDomestic birds have been bred from thefollowing orders: Galliformes (hens, quails,

turkeys, and pheasants), Anseriformes (ducksand geese), Columbiformes (pigeons),Passeriformes (canaries), and Psittaciformes(parakeets and parrots). In poultry farming, theyare divided according to their use: barnyard birds(Galliformes, Anseriformes, and Columbiformes)and companion birds or pets (Passeriformes andPsittaciformes). Commercial poultry farming ofbarnyard birds generates high revenuesworldwide. Farmers can take advantage of thefact that birds are very active during the day,that they readily live in groups, and that theyhave a high reproductive rate due to polygamousbehavior. Pets have commercial appeal, withtheir colorful plumage, ability to expressthemselves, and friendliness toward humans.These characteristics make them much-appreciated pets.

CAGEDCanaries, native tothe Canary Islands,have been selectivelybred by humans fornearly four centuries.

The breeding of birds in captivity has great social andeconomic value. This activity is carried out all over the worldon industrial poultry farms and family farms where birds are

raised for consumption and sale. A great variety of domestic birdshave been developed from species inhabiting natural environments.We use their flesh and eggs as food and their feathers in coats toprotect us against the cold. We also use birds for communicationand as colorful and melodic pets. They are so dependent on peoplethat in some cases they cannot survive when they are freed.

This disease, also called avian influenza A,is caused by a virus whose strains havevarious levels of virulence. Itdisseminated from Asian markets, wherethe overcrowding of domestic birds iscommon. This promoted the spread of thedisease to wild birds. As of 2006, morethan 30 million birds had succumbed tothis disease. Cats, pigs, and human beingshave also been infected.

50%THE COMMOTION ANDFEAR OVER DISEASEHAVE REDUCED THEDEMAND FOR THECONSUMPTION OFDOMESTIC BIRDS INMAJOR EUROPEANCITIES BY HALF.

PATHS INTO THE BODY

BacteriaVirus

ConjunctivaRespiratory TractNeedlesSkinWounds

SIZE COMPARISON

Digestive TractUrogenital Tract

Since early civilization, people have affected the Earth's environment. The cuttingof trees in rainforests and woodlands has destroyed many bird habitats, the lossof which is the leading cause of bird extinctions today. Also, the introduction

of animals such as cats, dogs, and rats to new areas has created athreat for many bird species. Indirect poisoning withpesticides, the trafficking of exotic birds as pets, and the saleof feathers have done further damage to many species.Fortunately, all is not lost. The first step to conservingthe world's avifauna is to learn about theextinction of birds and its magnitude.

BIRDS 9190 HUMANS AND BIRDS

Endangered Species

Indian

Ocean

Pacific

Ocean


C E N T R A LA M E R I C A A F R I C A

A S I A

E U R O P E

Pacific

Ocean


Atlantic

Ocean

O C E A N I A

Although the responsibilityof human beings isundeniable, many speciesbecame extinct because ofnatural phenomena.However, all the extinctionsfrom the 18th century to dateare related to human activities.

0

20

40

60

80

100

120

Indonesia Brazil Colombia China Peru India Philippines Ecuador New Zealand

UnitedStates

118115

78 76 75

4235

2520

74

Birds of Prey

Granivorous Birds

1942

2Small quantities ofpoison in seedsaccumulate in largeramounts in birdsand othergranivorous animals.

1Pesticides aresprayed on cropsto eliminate pests,and they stick tothe seeds.

3Birds of prey eatthe granivores. Theincreasing use ofpesticides impactshunting birds themost.

EXTINCT BIRDS

POISONING

SAVING THE PEREGRINE FALCON FROM EXTINCTION

BIRDS OF THE WORLD

CLASSIFICATION OF RISK

There were 350couples ofperegrinefalcons in theUnited States.

SPECIES HAVE GONEEXTINCT SINCE THE18TH CENTURY.129

179At criticalrisk

4Extinct inthe wild

1,212Endangeredspecies

788Species about tobe endangered

7,775Non-endangeredspecies (or noinformationavailable)

679Vulnerable

350Endangered

Dodo fromMauritiusQuicklyexterminated bycolonizers andseafarers in the17th century

The Most Important CausesBirds are very sensitive to changes in their habitats,and this is the main cause of extinction (87 percent

of species are affected by it). Excessive hunting is anotherof the greatest dangers, affecting 29 percent of theendangered species in the world. The introduction offoreign species is yet another major danger, jeopardizing 28percent of species. In addition, the intervention of humanbeings through the destruction of habitats and theintroduction of pollution combined with the occurrence ofnatural disasters harms more than 10 percent of species.

Alarming DataFive percent of the planet's surfacehouses three fourths of endangered

species. This area coincides with tropicalregions where biodiversity is greater. Forthis reason, tropical countries top the listto the right. On some islands, theproportion of endangered birds is veryhigh: in the Philippines and in New Zealand,it includes 35 to 42 percent of avian fauna.

Pesticides

1960Peregrine falconsdisappeared in the wildbecause of excessiveuse of pesticides (DDT and dieldrin).

1970Falcons werebred in captivityat CornellUniversity, to beset free later.

1986850 birds wereset free in thesouthernUnited States.

Extinct in the WildSpecies survivingonly in captivity

Critical RiskExtinction isimminent

EndangeredFast-decreasingpopulation

VulnerableHigh risk ofextinction in the wild

SHELTERS AND SANCTUARIESFOR ENDANGERED BIRDS

LEGEND

PEREGRINEFALCON

CAMPBELL ISLANDTEALAnas nesiotisOnly 50 individuals remainbecause of the introductionof mammals to the island.

YELLOW-CRESTEDCOCKATOOCacatua sulphureaIn threegenerations, itspopulation fell by 80percent because ofhunting.

MANGROVE FINCHCamarhynchus heliobates There are about 100remaining species on theGalapagos Islands.

INDIAN VULTUREGyps indicusIts population hasdecreased significantlyas a result of theveterinary use ofdiclofenac. The vultureeats the carrion of animalstreated with this drug and becomes poisoned.

CALIFORNIA CONDORGymnogyps californianusUntil 1978, there were 30specimens in the wild. Bredin captivity, new specimenshave been set free since1993. Their adaptation isbeing studied.

California Everglades

Amazon

UNITED STATES

BRAZIL

MALAYSIAN COCKATOOCacatua haematuropygiaIt is estimated that there arebetween 1,000 and 4,000individuals remaining. It washunted indiscriminately.

Serengeti

TsavoPrinceAlbert

Wankie

Krüger

NahuelHuapí

WoodBuffalo

INDONESIA

HYACINTH MACAWAnodorhynchus hyacinthinusIt is estimated that 1,000 to9,000 specimens live inthe Amazon.

BENGAL VULTUREGyps bengalensisFrom 1996 to date, itspopulation has fallen by 95percent, especially in India.

COLOMBIA

CHINA

PERU

PHILIPPINES

ECUADOR

NEWZEALAND

ROYAL CINCLODESCinclodes aricomaelive on humid mountain ranges,at altitudes between 11,500 and15,000 feet (3,500–4,500 m).Their number is unknown.

OF THE EARTH'S SURFACE IS HOME TO ALLENDANGERED BIRD SPECIES.

20%

INDIA

Celebes

Most birds of preyare endangered bythe excessive use ofnonbiodegradablepesticides.

BirdLife InternationalIt monitors endangered species anddevelops conservation programs.

92 GLOSSARY BIRDS 93

Glossary

AdaptationChange in the body of a bird or anotheranimal that allows it to reproduce better ina given environment

Adaptive RadiationEvolution of an initial species, adapted to agiven way of life, into other species, eachadapted to its own way of life

AerodynamicHaving an appropriate shape to decreaseresistance to the air. Birds' bodies areaerodynamic.

AlulaeRigid feathers whose function is to decreaseair turbulence during flight

Amino AcidMolecule from which proteins are produced

AncestorProgenitor, more or less remote, that passesdown a set of characteristics to itsdescendants

Angle of AttackThe change in position of a bird's wing toincrease or decrease speed and altitudewhile hunting prey by air

ApterylaeNaked areas of the skin where feathers donot grow

AtrophySignificant decrease in the size of an organ.The wings of nonflying birds have undergoneatrophy during evolution.

BarbsThin, straight, parallel blades, perpendicularto the shaft. They resemble the leaves of apalm tree.

BillHard cover of a bird's mandibles; also calledthe bill.

BiodiversityVariety of species that live in a given naturalor artificial environment

Biogeographic RegionsGeographic regions that biologists analyzeto determine the distribution of animals andother living organisms, according to thegeographic conditions of a place. Migratorybirds usually travel through differentbiogeographic regions between winter andsummer.

BipedAero-terrestrial animal that walks on itsposterior limbs. Birds are bipeds.

BrinyWater sample or body of water containingbetween 0.08 and 4.25 ounces (0.5-30 g) ofsalt per gallon of aqueous solution

BronchusEach of the branches into which the tracheadivides. The syrinx originates in the bronchi.

CalamusThe lower part of the vane that is wider,hollow, and, in general, naked. The feather isattached to the skin through the calamus.

CamouflageA characteristic that enables the animal toblend into its environment. It allows theanimal to go unnoticed in the presence ofpredators.

CarnivoreAn animal that feeds on meat

CovertsLayers of contour feathers that provide abird's body and wings with support and anaerodynamic surface

CrepuscularActive at dawn or twilight, when there islittle light

CrestExtended or raised feathers located on theupper part of a bird's head

CropMembranous sac that communicates with abird's esophagus, where food is softened

Dermal PapillaStructure from which a feather develops. Itis composed of epidermal and dermal cells.

DisplayBehavior directed at attracting theattention of a partner. It can also be done tothreaten or distract another animal.

DistributionPlace where a species is located. It includesthe area the species occupies in differentseasons.

Down FeatherA very thin and light feather, similar to silk,that birds have underneath their externalplumage. Down feathers constitute the firstplumage of chicks.

EcosystemCommunity of living beings whose vitalprocesses are interrelated and developaccording to the physical factors of thesame environment

EggLarge rounded shell, laid by a female bird,

that contains a yolk and a white. Iffertilized, the egg has a tiny embryo thatwill develop into a chick (the chick feedsitself on the yolk and white). When ready,the chick will break the eggshell.

Egg ToothSharp calcium growth, in the shape of atooth, that forms on the tip of a chick's billduring the embryonic phase. The chick usesthe egg tooth to break its shell at birth.

EnvironmentThe natural conditions, such as vegetationand land, that surround animals andinfluence their development and behavior

EpiphysisEndocrine gland located below the corpuscallosum in the brain. It produces a hormonethat regulates sexual activity.

EvolutionGradual process of change that a speciesundergoes to adjust to the environment

ExtinctNo longer existing. Many bird species arenow extinct (for example, ictiornites).

FeatherEach unit of the covering (plumage) of abird. The feathers are composed of a hardsubstance called keratin. They have a longquill, to which two blades are joined. Theblades—formed by a great number of barbs,uniformly distributed—give the feather itsshape and color.

FertilizationUnion of the reproductive cells of a male anda female that will create a new individual

Field MarkNatural distinct feature or artificialidentification of an individual of a bird species

that helps ornithologists distinguish it fromother individuals of the same or other avianspecies

FledglingVery young bird that lives in the nest whereit was raised

FossilsVestiges of ancient creatures of differenttypes (vegetal or animal) on a stonesubstratum. Fossils can be found in thegeologic strata of the Earth's surface.

Gastric JuiceSet of fluids produced by the stomachglands of birds and other animals

GizzardMuscular stomach of a bird. It is veryrobust, especially in granivores, and it isused to grind and soften the food by meansof mechanical pressure. The food arrives atthe gizzard mixed with digestive juices.

GlandType of structure that is present in mostmulticellular living beings. It producessubstances that act either inside or outsidea bird's body.

GonadOrgan that makes male or female gametes.In birds, the testicles and ovaries aregonads.

GranivoreBird that feeds on seeds or grains. Manybirds are granivores (for example, parrotsand toucans).

Gular SacSkin fragment in the shape of a sac thathangs from the lower mandible of certainbirds (for example, pelicans)

CarrionThe remains of dead animals used as food bysome birds or other animals. Vultures arescavengers (i.e., animals that feed oncarrion).

Center of GravityPoint at which the sum of all thegravitational forces that act on a bodyconverge

CereThin skin layer that covers the base of thebill

ChickA baby bird that has just come out of theeggshell and that has not yet left the nest.Its diet and safety depend on its parents.

ChorionOne of the coverings that wraps the embryoof reptiles, birds, and mammals

ClassOne of the many divisions scientists use toclassify animals. Birds form a class of theirown.

ClimateAverage temperature, humidity, andpressure that determine the atmosphericconditions of a region and that are related toother geographic characteristics of thatregion

CloacaThe widened and dilatable final portion ofthe intestine of a bird or other animal inwhich the urinogenital tubes converge

CourtshipBehavior patterns that males and femalesfollow to try to attract partners

94 GLOSSARY BIRDS 95

HabitatNative or natural environment of an animalor plant

HatchingCracking of the eggshell so that the birdcancome out

HistologicRelated to tissues and their study. When theanatomy of a bird is studied, the tissues thatform the bird's organs are analyzed.

HormonesSecretion of certain glands that circulatesthrough the body. They excite, inhibit, orregulate the activities of organs or ofsystems of organs.

HornMade of horn or of a consistency similar tothat of horn. The bill of birds is hornlike.

HypophysisInternal secretion organ located at thehollow of the skull's base (called silla turca).It is composed of two lobes: one anteriorand glandular and the other posterior andnervous. The hormones produced by thehypophysis influence growth and sexualdevelopment, among other things.

HypothalamusRegion of the encephalon located at thecerebral base, joined to the hypophysis by anerve stem, in which important centers forvegetative life are found

IncubationThe act of keeping the eggs warm so thatthe embryos inside can grow and hatch.Usually the chick's parents use their ownbodies to warm the eggs, but some birds usesand or decomposing plants to cover them.

InsectivoreBird that eats insects as part of its diet

InstinctInnate behavior that a bird or other animaldevelops and that is not learned. Theoffspring of ducks start to swim by instinct.

InvertebrateAnimal that lacks a spinal column. Worms,crabs, and jellyfish are examples.

LethargySleep through which a bird can reduce itscardiac rhythm and its body temperature tosave energy, especially at night and duringextended periods of cold

Malpighian LayerLayer of epithelial cells that forms the bird'sepidermis

Mangrove SwampType of ecosystem often considered a typeof biome. It is composed of trees that arevery tolerant to salt. These trees are foundin the intertidal zone of tropical coasts.Areas with mangrove swamps includeestuaries and coastal zones.

MigrationThe movement of birds from one region toanother; it usually takes place in the springand fall. It is also common among otherspecies of animals.

MoltProcess through which birds lose old wornfeathers, replacing them with new ones

MonogamousBirds that mate with only one individual ofthe opposite sex. Many penguins havemonogamous behavior.

PiscivoreBirds living in continental or oceanic watersthat feed on fish

PollutionA consequence of human actions for naturalenvironments. The emission of industrialgases into the atmosphere, for example,produces pollution.

PolygamyReproductive relationship between oneanimal of one sex and several animals of theother. When one male mates with severalfemales, it is called polygyny. Only rarely dofemales have multiple male reproductivepartners (polyandry).

PopulationSet of individuals of the same species thatlive together in the same space at the sametime

PredatorAnimal that hunts other animals. Birds ofprey hunt other birds, mammals, andvertebrates.

PreyAnimal hunted by another to serve as foodfor the latter. Animals that hunt prey arecalled predators.

ProteinOrganic macromolecule that is part of livingbeings. By including proteins in their diet,birds get the necessary amino acids to buildtheir own organs.

Protein CordEmbryonic structure: each of the twofilaments that sustain the yolk of the eggwithin the white

ProventriculusThe first portion of the stomach, or the true

stomach, of a bird. The other portion of abird's stomach is the gizzard.

RectricesTechnical term used by ornithologists todescribe a bird's tail feathers

ScaleDermic or epidermic layer that totally orpartially covers the feet of birds. They arereptilian vestiges.

SongSound or series of sounds produced by abird to demarcate its territory or to find amate. The songs of birds can be simple orelaborate, and some are very melodic.

SongbirdsSinging birds. Passerines include songbirds.

SpeciesSet of individuals that recognize themselvesas belonging to the same reproductive unit

SternumCentral chest bone. The sternum of flyingbirds has a large surface in which musclesare inserted.

SurvivalA bird's ability to face the demands of itsenvironment and of intra- and interspeciesrelationships

SwampDepression on the ground in which water isgathered, sometimes called a marsh. Itsbottom is more or less boggy. It is thehabitat of many wading birds.

ThermalHot air current that rises. Many birds makeuse of it to gain height effortlessly.

TheropodsGroup to which carnivorous dinosaursbelong

TrainingTeaching an animal new skills. Carrierpigeons are trained.

TundraVast plains without trees in the Arcticregions of northern Asia, Europe, and NorthAmerica

Uropygial GlandProduces an oily secretion that birds, usingtheir bills, spread on their feathers to makethem impermeable

VertebrateAnimals that have a spinal column, such asbirds, fish, reptiles, amphibians, andmammals

VirusInfectious agent that depends on a livingbeing to reproduce. Avian flu is transmittedthis way.

VulnerableBirds that are endangered in their naturalhabitats

YolkYellow part of the egg. If the egg isfertilized, a small embryo grows that willuse the yolk (and white) as food.

YoungBird or any other animal at an early stage oflife. Some young show color patterns thatare very different from that of adults of thesame species, which makes it difficult forpredators to identify them.

MorphologyStudy of the form of an object or structure.For instance, the morphology of the feet ofbirds is an area of study.

NectarSweet and sugary secretions found inflowers that attract birds and other animals.Hummingbirds feed on nectar.

NidicolousA helpless chick that depends on its parents'care after birth

NidifugousA chick that can move and leave the nest assoon as it breaks its shell. In less than a day,such chicks can move agilely.

NocturnalActive at night. Many birds of prey, such asowls, specialize in nocturnal hunting.

NutrientAny substance obtained through diet thatparticipates in the vital functions of a livingbeing.

OmnivoreBird that has a varied diet, including animaland vegetal foods

PelagicBirds that live in areas over open waters,away from the coast

Pellet (Bolus)Small, hard mass that some birdsregurgitate (vomit). It contains parts of thefood that they could not digest, such asbones, fur, feathers, and teeth.

PigmentSubstance that colors the skin, feathers, ortissues of animals and plants

96 INDEX BIRDS 97

Index

Aadaptation

aquatic life, 5cellulose digestion, 57environment, 66flightless birds, 29flying, 8f, 12, 24-25foot, 20-21hatching, 53marine birds, 70, 71perching, 13, 79swimming, 68urban habitats, 83walking, 7

adaptive radiation, 62aero-terrestrial habitat, 65African ostrich

flightless birds, 68-69weight, 8

Afrotropic region, 67albatross

birth, 52classification, 64gliding, 35incubation (egg), 52migration routes, 59wings, 29

altitudinal migration, 58anatomy

external features, 8-9internal organs, 14-15skeleton and musculature, 12-13See also specific body parts by name, for example, wing

ankle, 21annual life cycle, 42-43Anseriformes (bird classification), 64, 72Antarctic bird: See penguinapteria, 27Apterygiformes (bird classification), 65, 69aquatic bird

classification, 64, 65foot adaptation, 20

physical adaptations, 5powder down, 27See also marine bird

arboreal theory (evolution), 24Archaeopteryx, 10-11arctic tern, migration, 39, 58aricari, bill, 19artery, 15Asia

bird domestication, 89migration routes, 59

Australasia, 67Australian bowerbird, courtship behavior, 46avian influenza A, 88Aztec culture, 82

Bbald eagle

birds of prey, 74talons, 21

bar-headed gooseflight altitude, 38 migration routes, 59

barn swallow, migration, 58, 59, 79bat, wing, 24beak: See billBengal vulture, 91bill, 18-19

birds of prey, 74ducks, 73food filtration, 56identification, 9modern bird, 12parrot, 76

binocular vision, 17binoculars, 84biodiversity

endangered species, 90-91geographical regions, 66-67running birds, 69

biogeographic region, 66-67bird flu: See avian influenza A

Caspian tern, migration routes, 59Casuariiformes (bird classification), 65, 69Central America, migration routes, 58Charadriiformes (bird classification), 64, 65, 73China, birds in symbolism, 82chough, flight altitude, 38circulatory system, 15classification, 64-65claw, 21climbing, foot adaptation, 20cockatoo, endangered species, 91collarbone

Archaeopteryx, 11modern bird, 12-13

coloration, 77flesh, 12seasonal changes, 32

common loon, 70common spoonbill, feeding, 73common waxbill, 20communication, 44-45compass-and-triangulation system

(migration), 59condor

captive breeding, 90dimensions, 75

contour (feather), 26coracoid, 13courtship, 46-47

annual life cycle, 43black grouse, 31hummingbird, 37tail feathers 30

covert (feather), 26crane

courtship behavior, 47migration routes, 59

crop (esophagus), 14crossbill, bill, 19curlew sandpiper, migration routes, 59cursory theory (evolution), 24

DDarwin, Charles, 10data collection, 85defense

camouflage: See camouflageclaw, 21individual behavior, 60group behavior, 61

diet, 56-57adaptation of bill, 18courtship food, 46dive fishing, 71flight needs, 36-37nidicolous birds, 55nidifugous birds, 54Universe of Birds, 5

digestive process, 14digestive system, 14-15dinosaur fossil, 10diurnal bird of prey, 74

See also specific birds by name, for example,eagle

diving bird, 73dodo, 91domestication, 88-89dove, symbolism, 83down (feather), 26duck

feeding, 62, 72human consumption, 88swimming mechanism, 72

dust bath, 27

Eeagle

birds of prey, 74-75carrying ability, 25feeding strategies, 57migration routes, 59speed, 39

symbolism, 82-83talons, 20, 21

earexternal anatomy, 9senses, 16

egg, 50-51incubation, 52

egg tooth, 53Egyptian mythology, birds in symbolism, 82-83eider, flight speed, 38embryo formation, 50-51endangered species, 90-91epiphysis: See pineal glandequipment, bird watching, 84-85esophagus, crop, 14Eurasian eagle owl, 74Europe, migration routes, 58-59evolution, 10-11

flight adaptation theories, 24excretory system, 14extinction, risk, 91

See also endangered specieseye, 17eyesight: See vision

Ffalcon

bill, 19speed, 39urban habitats, 86

falconry, 82false knee: See anklefarm production, 88-89feather

camouflage, 60color, 77external anatomy, 8-9flight, 26-27growth and molting, 32-33human uses, 83parrot, 22-23seasonal color changes, 32

bird of prey, 74-75pesticide poisoning, 90vision, 17

birdcall, communication, 44warnings, 61

birdsong, communication, 44-45birdwatching, 84black grouse, courtship display, 31black swan, flight speed, 38blackbird, urban habitats, 87blood circulation: See circulatory systemblue-and-white swallow, 80blue-footed booby, courtship behavior, 43bone: See skeletal systembrain

Archaeopteryx, 10sound production, 44

breathing: See respiratory systembrown pelican, 70Bubo capensis, 6, 7Buffon, Georges-Louis Leclerc, Count de, 66

CCalifornia condor, captive breeding, 90call: See birdcallcamera, 84camouflage

defense strategies, 60molting, 32

Campbell Island teal, 91canary, 88cannon net, 85Cape gannet

marine birds, 70migration routes, 58

captive breeding, 90carnivorous bird

gizzard, 14See also bird of prey

carpal bone, 13carpometacarpus, 13

98 INDEX BIRDS 99

tail function, 30See also tail

feeding strategy, 57femur, 13finch, 90fish, in diet, 57fishing method, 71flamingo

bill, 19food filtration system, 56milk feeding, 56-57

flapping flight, 36-37flapping wing, 12flight, 22-39

adaptations and mechanisms, 8, 12diet, 56-57oxygen needs, 14See also wing

flight pattern, 35flightless bird, 68-69

geographic distribution, 67wings, 29

flying animal, 25foot, 20-21

Archaeopteryx, 11birds of prey, 75external anatomy, 9marine adaptations, 70perching adaptations, 13, 79skeleton and musculature, 13zygodactyl, 77

fossil recordbones, 24German findings, 10

freshwater bird, 72-73frigatebird, reproductive season, 43fruit, in diet, 57fulvous whistling duck, 72-73furculum: See collarbone

GGalliformes (bird classification), 65, 69

geographic distribution, 66-67Passerines, 79

Germany, fossil findings, 10gizzard, types, 14gliding, 34-35golden plover

flight endurance, 39migration routes, 58

goosedomestic breeds, 88flight altitude, 38flight pattern, 35

goshawkbirds of prey, 74courtship behavior, 46

grain food, 57granivorous bird, gizzard, 14grasping mechanism, 13

foot adaptation, 20great crested grebe

courtship behavior, 46lobed toes, 21

greenfinch, bill, 19grey crowned crane, courtship behavior, 47group defense behavior, 61growth stage

nidicolous birds, 55nidifugous birds, 54

gull herring gull, 70urban habitats, 86

Hhabitat, 65

destruction, 90direct observation, 84terrestrial, 65urban habitats, 83, 86-87woodpecker, 76See also aquatic bird; freshwater bird;

marine birdhammerkop, feeding, 73

captured birds, 85See also classification

imperial heron, 27imperial shag, 70incubation (egg), 52incubator bird, 54India

domestication, 89representation of god, 82

Indian vulture, 91Indomalaya region, 67insectivore, 57

Jjaw, 19jawbone, Archaeopteryx, 10Jurassic Period, Archaeopteryx, 10-11

Kkeratin, 27kiwi, 69knee, 21

Llatitudinal migration, 58laying (egg): See eggLeclerc, Georges-Louis, Count de Buffon, 66leg, 20-21

grasping mechanism, 13muscles, 13

lek ritual, 46lesser spotted eagle, migration routes, 59life cycle, annual, 42-43little masked weaver, nest building, 49longitudinal migration, 58loon: See common loon

lung, 15lyrebird, 78

MMalaysian cockatoo, 91mangrove finch, 90marine bird, 65, 70-71

gliding, 35See also aquatic bird

marine glider, 34marking (captured bird), 85Mayan culture, 82meat, in diet, 57metabolism, 9Mexico, domestication, 89migration, 58-59

artic tern, 39Passerines, 79Universe of Birds, 4-5

mimicry of sound, 76, 78, 79mist net, 85molting, 32-33monocular vision, 17monogamy, 47musculature, 12-13mythology, 82-83

Nnasal marker, 85Nearctic region, 66neck marker, 85nectar, 57Neotropic region, 66nest

construction, 49types, 48

nesting, 5partridge, 41

net, types, 85

nidicolous bird, 54, 55nidifugous bird, 54nocturnal bird, 74

See also owlNorth America

indigenous peoples, 83migration routes, 58

northern harrier, courtship behavior, 46northern wheater, migration routes, 59nostril, 71nuptial display: See courtship

OOceania, 66Origin of Species, The (Darwin), 10ornithology, 84-85ostrich

African ostrich, 8, 68-69distribution, 67

ovenbird, 79owl

birds of prey, 74Bubo capensis, 6-7diet, 57urban habitats, 86

oxygen, consumption, 14

PPalearctic region, 67parental care (evolution), 24parrot

feathers, 22-23flight speed, 38talking birds, 76

partridgenesting, 41red-legged partridge, 54

passerine (Passeriformes), 78-79external anatomy, 9

hatching, 52-53postnatal development, 54-55See also egg

hatching muscle, 53hawk, bill, 74hearing, 16heart, 15Heligoland trap, 85heron

bill, 19feeding, 73imperial heron, 27tricolored heron, 20-21white heron, 4, 5

herring gull, 70hoatzin, 64, 66Holarctica, 67human anatomy

comparison, 10leg, 21vision compared, 17

human interaction, 82-83domestication, 88-89

humerus, 13hummingbird

bill, 19courtship behavior, 37external anatomy, 12flight mechanism, 37internal organs, 14-15migration routes, 58Passeriformes, 78ruby-throated hummingbird, 58, 67tongue, 57wine-throated hummingbird, 8

hunting bird: See bird of preyhyacinth macaw, 90hypophysis, 42

Iibis, 73identification, 9

100 INDEX

classification, 64, 65pelican

brown pelican, 70flight, 34-35resting pose, 42-43

pelvis, Archaeopteryx, 11penguin

external anatomy, 8feather coverage, 27incubation (egg), 52mating behavior, 47molting, 32observation, 85swimming adaptations, 68swimming speed, 39

perching foot adaptation, 20skeleton and musculature, 13See also passerine

peregrine falconmigration routes, 58pesticide poisoning, 90speed, 39

pesticide, poisoning, 90pheasant, flight speed, 38pigeon

incubation (egg), 52messenger service, 88milk feeding, 56-57skeleton, 10urban habitats, 83, 86wing mobility, 11

pineal gland, 42plumage: See featherpneumatic bone, 13Podicipediformes (bird classification), 65, 73polyandry, 47polygamy, 47polygyny, 47population control, urban habitats, 87postnatal development, 54-55poultry farming, 88-89powder down, 27preening, 27ptarmigan, molting, 32

pterodactyl, wing, 24pterylae, 27puffin, 66pygostyle, 11, 13

See also tail

Q-Rquetzal, 76, 82radius, 13ratite, 69raven, 19, 78religion, birds as symbols, 82-83reproduction

courtship: See courtshipegg, 50-51hypophysis, 42

reptile, bird evolution, 24respiratory system, 15rhea, 69ribs, Archaeopteryx, 11ringed bird, 85robin, 80-81, 87rockhopper penguin, 68royal cinclode, 90royal eagle, speed, 39royal swift, flight speed, 38ruby-throated hummingbird

bird distribution, 67migration routes, 58

ruff, courtship behavior, 43running bird

flightless birds, 69foot adaptation, 20

running theory (evolution), 24Ruppell's griffon vulture, 39

Ssalt gland, 71scale (bird skin)

feet, 21types, 25

Scots dumpy rooster, spurs, 21seagull, urban habitats, 86seasonal color change, 32seed food, 57seizing: See grasping mechanismsense, 16-17

external anatomy, 9shoebill, feeding, 73Siberian crane, migration routes, 59sight: See visionskeletal system, 12-13

Archaeopteryx, 11legs, 21running birds, 69See also under specific topic, for example toe

skullArchaeopteryx, 10modern bird, 12

sleep regulation, 42smell, 16snow bunting, migration routes, 58snowy egret, courtship behavior, 46song: See birdsongsongbird

classification, 64, 65distinction, 9Passeriformes, 78-79

sound productionrecording, 84songbirds, 78, 79talking birds, 76

South Americadomestication, 89migration routes, 58species diversity, 66

sparrowurban habitats, 83, 87white-throated sparrow, 8-9

sparrowhawk, 74species classification: See classificationspeed, 38-39spin tailed swift, speed, 39spine

Archaeopteryx, 10bones, 13

spoonbill: See common spoonbillspur, 21stability, 8starling

defense formation, 61flight speed, 38

sternum, modern bird, 12-13stork

feeding, 73flight speed, 38migration routes, 58urban habitats, 86

Struthioniformes (bird classification), 65, 69swallow, 78, 79, 80swan

flight altitude, 38migration routes, 59

swift, urban habitats, 86symbolism, 83syrinx, sound production, 44, 79

Ttail, 30-31

Archaeopteryx, 11pygostyle, 11, 13

tail feather, 8talon, Archaeopteryx, 11tarsometatarsus, 13

Archaeopteryx, 11terrestrial animal, speed of movement, 39terrestrial glider, 34, 35terrestrial habitat, 65territorial demarcation, 45theropod, 10thigh, 21tibia, 13, 21tibiotarsus, 21toe

anatomy, 9, 13Archaeopteryx, 11

types, 20tongue

hummingbird, 57internal organs, 15, 16

toucanbill, 19colorful birds, 76

touch, 16Triassic Period, theropodan reptile, 10tricolored heron, 20-21turkey, 88

U-Vulna, 13urban habitat, 83, 86-87vein, 15velociraptor, 10vibrissae, 27vision, 16, 17vulture

endangered species, 91feeding practices, 75flight altitude, 39

Wwading bird, 73walking bird, adaptations, 7, 20wandering albatross

migration routes, 59distances, 40wings, 29

water absorption, 14waxbill: See common waxbillwhite heron, 4, 5white stork, migration routes, 58white-throated sparrow, 8-9wide bill, 79wine-throated hummingbird, 8wing, 28-29

birds of prey, 75feathers, 9gliding, 34-35markers, 85skeleton and musculature, 12-13types and evolution, 24

wing loading, 29winglet, 34wingspan, 29woodpecker, 76wrist joint, Archaeopteryx, 11

Y-Zyellow-crested cockatoo, 91zone-tailed hawk, 74-75

BIRDS 101

Bisl 10 birds

Education

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