Contents

Flying Beasts 4

The Age of Archosaurs 6

A Different Earth 8

Adapting to Change 9

Bird Fossils 10

Revealing Evidence 12

Ornithologists 13

Bird Groups 14

Birds Closeup 16

Life Cycle of Birds 18

Feeding Habits of Birds . . . . 20

Disappearing Act 22

Prehistoric Birds Onscreen . . 24

Digging for Birds 26

Further Research 28

Ancient Activity . . . . . . . . . . 29

Quiz 30

Glossary 31

Index 32

Flying Beasts

B irds have lived on Earth for a long time. When

dinosaurs roamed the world, prehistoric birds also

filled the skies. Scientists think the first birds appeared

on Earth about 150 million years ago, during the Late

Jurassic Period.

There were many types of prehistoric birds. Theyranged in size from very small to very large. Manydied out along with the dinosaurs at the end of theCretaceous Period, about 6^ million years ago. Eventhough many birds disappeared, others continuedto live and are still living today.

Pterosaurs were flying reptiles, not birds. They had wings, but nofeathers. A leather membrane covered their wings. Their wingsranged in size from a few inches to more than 40 feet (12 m).

4 FLYING BEASTS

Albertosaurus\N3S a theropod, which means "beast footed."Most theropod dinosaurs walked on two legs.

Today, many paleontologists believe that birdsactually evolved from a type of dinosaur called atheropod. Theropods were meat-eating dinosaursthat shared many features with modern birds.

FACTS ABOUT FLYING ANIMALS

The largest known flying animalwas Quetzacoatlus, a memberof the pterosaur family, it hada wingspan of 40 feet (12 m) ormore. Quetzacoatlus \N3sf'\[s\discovered in Big Bend NationalPark, Texas, in 1971.

• Some scientists are not sureif the Archaeopteryx, the firstknown bird, used its feathersto keep its body temperaturenormal or if it used its feathersfor flight.

BIRDS 5

The Age ofArchosaurs

For more than 3.5 billion years, living things have

grown and developed on Earth. Scientists have

divided Earths history into blocks of time called

eras. The eras are divided into periods. The dinosaurs

lived during the Mesozoic Era, often called the "Age

of Dinosaurs."

PRECAMBRIAN ERA

Algae fossils

4.6 Billion to 545 MillionYears Ago

During the Precambrian Era,simple life forms firstappeared in the seas.

PALEOZOIC ERA

545 Million to 250 MillionYears Ago•̂ Paleozoic means "ancient life."

During this era, more complexlife forms appeared on Earth,including fish, insects, landplants, and reptiles.

Trilobite fossils

6 THE AGE OF ARCHOSAURS

Some scientists think the Mesozoic Era should be

called the "Age of Archosaurs." The archosaurs were a

large group of animals that included birds, dinosaurs,

and pterosaurs, or flying reptiles.

The first known bird was the Archaeopteryx. It is

thought to have appeared at the end of the Jurassic

Period about 150 million years iigo. The Archaeopteryx

shared features with the birds that are alive today and

dinosaurs. It had bird-like features, such as feathers,

wings, a wishbone, and light, hollow bones. It also

had dinosaur-like features, such as a full set of teeth,

a long tailbone, and three claws on each wing.

MESOZOIC ERA CENOZOIC ERA

Brontotheres sk\.\\\

250 Million to 65 MillionYears Ago• Mesozoic means "middle

life." Dinosaursand birdsappeared during the MesozoicEra. By the end of this era,many of these animalsbecame extinct.

65Million Years Agoto the Present

Cenozoic means "recent life."All types of mammals beganto appear on Earth during theCenozoic Era.

Oldest-known hat fossil

BIRDS 7

A Different Earth

D uring the Mesozoic Era, when birds first

appeared, Earth was much warmer than it

is today. In the Triassic Period, the land on Earth

formed one large continent called Panguea. The

climate was warm, the sea level was high, and there

was no ice at the North Pole or South Pole. During

the Jurassic Period, Pangaea began to divide into

separate continents. The climate grew moist, and

forests became thicker. In the Cretaceous Period,

the land continued to shift and change. The climate

was warm, and there were wet and dry seasons. By

the end ofthe Cretaceous Period, the continents

looked much like they do today.

THE CHANGING CONTINENTS

Triassic PeriodOne continentcalled Pangaea

Jurassic PeriodPangaea beginsto break apart

Cretaceous PeriodModern continentsbegin to form

8 A DIFFERENT EARTH

Adapting toChange

The Doc/o did not needto fly, so it developedsmall, weak wings.

DODO

The Dodo'shooked beakmay havebeen usedto catch fish.

The Dodolacked thestrong chestmuscles neededfor flight.

As Earth changed, animals adapted to fit intotheir environment. Paleontologists agree that

the first bird was the Archaeopteryx, but after that, theydisagree about the history of birds. Some scientiststhink that birds evolved from meat-eating dinosaurscalled theropods. Today's birds share many features withancient theropods, including light, hollow bones. Otherscientists believe that birds evolved from early reptilescalled thecodonts. Crocodiles, dinosaurs, and pterosaursall evolved from archosaurs.

BIRDS 9

Bird Fossils

P rehistoric birds lived on Earth a long time ago.

It is not possible to go back in time to see them.

It is possible to learn about them by looking at their

fossils. Fossils are the rocklike remains of ancient

animals and plants. Some fossils are bones and shells,

and other fossils are impressions of feathers, leaves,

and skin. Feather impressions found in ancient rocks

have helped scientists identify prehistoric birds such

diS Archaeopteryx.

Hardened tree sap, also called amber, can preserve items so well thateven the individual fibers of a feather are visible.

10 BIRD FOSSILS

T T M ' I '

Sedimentary rock, where many fossils are found, is made of strata,or layers. Exposed sedimentary rock often can be found on cliffs andriverbanks or in desert badlands.

HOW FOSSILS ARE FORMED

Paleontologists have found thefossils of many different prehistoricanimals. A fossil is created whenlayers of mud and sand cover thebones of an animal that has died.As time passes, layers of mud buildup. The weight of the upper layersof mud pushes down on the lowerlayers to form solid rock. Bones orplant materials become fossils.

Bird fossils afe not as common asdinosaur fossils. Birds had light,hollow bones that did not alwayslast long enough to become fossilsAfter a bird died, it sometimes rottedaway or was eaten by other animalsbefore its bones could get trappedin mud.

BIRDS 11

RevealingEvidence

Every new fossil helps paleontologists understand

what life was like on Earth long ago. By looking at

fossils, scientists can get a better idea of how large an

animal was, when it lived, whether it walked on the

ground or flew through the air, and if it lived alone

or in a herd. Paleontologists are much like detectives.

They try to learn as much as they can from the evidence,

or clues, they find.

In order to identify a bird fossil, paleontologists look

for special features, such as impressions of feathers, a

wishbone, or bird-like hips. These

are the features that prehistoric

birds such zs Archaeopteryx had

in common with modern birds.

Scientists think thatArchaeopteryxy^3s a weakflier. It probably was best atgliding, leaping, and running.

12 REVEALING EVIDENCE

CAREER LINK

Ornithologists

A n ornithologist studies birds. They may study

the behavior of birds, where birds live, and how

birds interact with their environment. Ornithologists

may also be involved in saving birds that are in danger

of becoming extinct. Ornithologists can work for

government agencies or other organizations. They

may work with wild birds, in a laboratory, or on their

computer. Some study a particular bird group, while

others are interested in all birds. Ornithologists perform

many different types of jobs, and they use a variety of

tools. If they work in the field, they may use binoculars,

telescopes, and nets or traps. If they work in a laboratory,

they may use microscopes, test tubes, cages, and

computers. To become an ornithologist, you need

to do well in science and math classes. You should

also develop the language

skills necessary for

writing reports.

Ornithologists sometimes catchand tag birds in order to tracktheir migration patterns.

BIRDS 13

Bird Groups

B irds can be divided into two major groups: theadvanced fliers and the flightless birds. Scientists

believe that the type of dinosaur most closely relatedto birds is a group of dinosaurs called theropods, agroup of bipedal dinosaurs. Theropods share so manyfeatures with today's birds that some scientists believethat birds actually are theropod dinosaurs. One verybird-like dinosaur was the Deinonychus. This dinosaur

did not have feathersand could not By, but itsdistinctive hipbone issimilar to the hipbone ofa modern bird. This hasled scientists to believe thatmodern birds evolved fromDeinonychus, or a dinosaur

very much like it.

The hipbone of theropods allowedthem to stand and walk upright.Modern birds have the same typeof hipbone.

14 BIRD GRDUPS

ADVANCED FLIERS: NEOGNATHOUS BIRDS

Most modern birds belongto the neognathous, or advancedfliers, group. Many scientistsbelieve that all birds developedfeatures for flight Birds neededto be very light to get off theground and stay off the ground,so they developed hollow bones.They also needed to stay in theair once they were in the air.That is why birds developedwings and feathers.

How Deinonychusïr]\qhX havedeveloped into an animal thatcould fly is still a mystery toscientists. Some believe thatDeinonychus ran quickly and

flapped its arms to get into theair Others think that the smalltheropod gradually developedwings in order to glide fromtree to tree. The discoveryof the Microraptorgui'm Chinasupports this theory. Thissmall flying dinosaur hadfour wings—one on eacharm and leg.

FLIGHTLESS BIRDS: PALAEOGNATHUS BIRDS

There are still a few speciesof palaeognathus, or flightless,birds alive today. Scientiststhink that flightless birds losttheir ability to fly becausethey were not threatened bydangerous predators. They hadno reason to leave the ground.

Flightless birds stillexist in places suchas Africa, Australia,New Zealand, andSouth America.

Ostrich

BIRDS 15

Birds Cioseup

M any different kinds of birds lived in prehistoric

times. Some were the size of a chicken, while others

had 25-foot (7.5-m) wingspans. There were birds that

stood 12 feet (3.7 m) high and others that weighed 800

pounds (363 kg). There were flightless birds and birds

that could fly.

Diatryfna was first discoveredin 1874 in New Mexico.Diatryma was a large,flightless, meat-eating bird.It lived 53 million years ago.

16 BIRDS CLDSEUP

ARCHAEOPTERYX

• Believed to be the first bird• Same size and weight as

a crow• Appeared in the Late

Jurassic Period• Probably ate insects

and small plants• Shared many

characteristics withboth birds and reptiles

I•

MOA

Extinct flightless bird thatlived in New ZealandFirst appeared 82 rriillionyears agoCould reach 12 feet (3.7 m)and weigh more than 660pounds (299 kg)A plant-eaterExtinction caused by earlyhumans in New Zealand

AEPYORNIS

• Flightless bird• Stood 9 feet (2.7 m) high

and weighed more than8Ü0 pounds (363 kg)

• Seven species lived onthe island of Madagascar;some survived until theseventeenth century

• Had tiny wings and long,sturdy legs

ANOALGALORNIS

Large, meat-eating,flightless bird that livedin South AmericaPeaked in numbers duringthe Tertiary Period, 65 to1.8 million years agoRan fast and had largehooked beakReplaced by otherpredators such asthe jaguar and puma

DOOO

About the size of alarge turkeyA flightless memberofthe pigeon familyHad short legs, a largebeak, and tiny wingsKilled by European sailorsfor food and spoitBecame extinct about 1680

ARGENTAVISHad a 25-fnot(7-6 mjwingspanWeighed 265 pounds(120 kg)Lived about 5 to 8 millionyears agoAncestor ol some vulturesand storksThought to be a veryfierce predator

BIRDS 17

Lile Cycleof Birds

L ike reptiles and dinosaurs, birds lay eggs. Prehistoric

bird eggs came in many shapes and sizes. Some were

tiny. Others were very large. The size of the egg would

usually depend on the size of its mother.

It is rare to find fossilized eggs because they are veryfragile. The largest bird egg fossil ever found belongedto iheAepyomis, or elephant bird. This enormous birdproduced an equally enormous egg—it weighed22 pounds (9.9 kg). Sometimes, whenpaleontologists find a fossilized egg,they discover a tiny, fossilized embryoof a bird inside. This is unusual andvery special.

quail egg chicken egg ostrich egg elephant bird egg

18 LIFE CYCLE OF BIRDS

The tiny hummingbird lives from 3 to 5 years. The large ostrich canlive for 75 years.

Scientists do not really know how long prehistoric birds

lived. The length of a prehistoric bird's life was probably

different for each species of bird. Some scientists believe

that prehistoric birds lived as long as modern-day birds.

Paleontologists believe that larger animals lived longer

lives than smaller ones. Large birds, like New Zealand's

moa, might have hatched out of an egg, grown up, and

lived a much longer life than the small dodo, another

flightless bird.

EGGS FOR LUNCH?

Laying eggs might have led to theextinction of some prehistoric birds,such as the Diatryma. Because theDiatryma laid its eggs on the ground,

other animals could easily find andeat them. Paleontologists think thisis why the Diatiyma became extinct.

BIRDS 19

Feeding Habitsof Birds

Even though birds probably evolved from meat-eating

dinosaurs, some became meat-eaters, while others

became plant-eaters. Some birds, such as the moa,

were large, slow-moving, plant-eating birds. The moa

is thought to have eaten fruits, seeds, and vegetables.

Other birds, such as the Argentavis,

were meat-eating birds. They had

powerful legs that allowed them

to run very fast. Once they caught

their prey, they could easily tear it

apart with their sharp talons and

hooked beak.

N A new species of puff bird wasdiscovered in Lincoln County, Wyoming.It lived approximately 50 million yearsago and likely ate insects, just likemodern puff birds, which live in tropicalNorth and South America.

2 0 F E E D I N G H A B I T S OF B I R D S

Food Weh

SUN

DECAYINGBIRD

REMAINS

PLANT-EATING BIRDS

MEAT EATINGBIRDS

FOOD WEB

Just like life today, all life inprehistoric times relied on anexchange of energy, also calleda food web. For birds, this foodweb began with plants. The plantsmade their own food by convertingthe Sun's rays into energy. Theseplants were eaten by herbivores,

or plant-eaters. The herbivores wereeaten by carnivores, or meat-eaters.When a bird or any other living thingdied, its body would break down andprovide food for plants.

BIRDS 21

Disappearing Act

A lmost half of the worlds animal and plant species

became extinct at the end ofthe Cretaceous Period.

Some scientists think these animals and plants became

extinct because the climate became colder. Other

scientists believe that a huge meteorite

crashed into Earth and hurled tons of

dust into the air. The dust formed a

thick cloud that blocked out light from

the Sun. Soon, plants died because

they could not get enough sunlight.

Plant-eating animals starved

to death. Losing their prey,

meat-eating animals

died, too.

The dodo evolved into a non-flying bird after settlingon the island of Mauritius in the Indian Ocean. Theintroduction of new animals onto the island and theuse of the dodo for food caused it to become extinctby the 1680s.

22 DISAPPEARING ACT

Although birdfossils are notas common asdinosaur fossils,many of themcontain detailsthat are helpingscientists explainhow birds evolved.

Many different species of birds had developed

by the end ofthe Cretaceous Period. Some

disappeared in the mass extinction, although

paleontologists are not sure how many species

became extinct. Hesperornithiform birds, which

were flightless birds that spent most of their time

in water diving for food, disappeared with the

dinosaurs, ¡chthyornis, z fiying bird with teeth,

also disappeared about the same time. Although

primitive birds with teeth disappeared at the end

ofthe Cretaceous Period, many toothless birds

survived this mass extinction. The birds that

survived the great extinction eventually developed

into the land birds and water birds of today.

AN OLD THEORY OF EXTINCTION

Early scientists once believedthat ancient warm-bloodedanimals, the ancestors ofmodern-day mammals,were responsible for thedisappearance of the dinosaurs.

According to this theory,small, furry animals ateall of the dinosaur eggs.Today, this theory isasextinct as the dinosaurs.

BIRDS 23

Prehistoric BirdsOnscreen

I n modern culture, dinosaurs receive most of the

attention given to prehistoric animals. They are

everywhere^on television, in movies, in books,

and on cereal boxes. Prehistoric fliers do not appear

nearly as often in books and movies.

Pterosaurs are popular characters in movies and television shows suchas Jurassic Park III, Dinotopia, The Flintstones, and The Lost World

24 PREHISTORIC BIRDS ONSCREEN

Flying animals do appear in movies, but most of these

animals are flying reptiles. In 1933, a scary-looking

pterosaur was featured in the movie King Kong, This

enormous creature tried to pull Fay Wray, the lead

character, off a cliff.

Many prehistoric birds

looked like the birds

seen today. Instead

of waiting to see a

prehistoric bird on

a movie screen, just

go birdwatching.

Unlike their prehistoricancestors, modern meat-eatingbirds do not have teeth and haveto tear their food apart withtheii beaks.

YABBA DABBA DOO!

In the cartoon, The Flintstones,cartoon people live amongdinosaurs. In the cartoon,people strapped seats to thebacks of pterosaurs and usedthem as airplanes. TheFlintstones also usedprehistoric birds asfeather dusters.

BIROS 25

Digging for Birds

I t is unusual to find fossils of flying animals because

their bones are light and easily destroyed. Even so,

paleontologists niake exciting discoveries every year.

This map shows some exciting discoveries of prehistoric

birds and flying reptiles.

In 1872, Benjamin F.Mudge found the firstIchthyornisiossW inKansas. The fossils ofseveral species of thisgull-sized bird havebeen found all overNorth America.

In the mid-nineteenth century,fossils of giant flying reptileswere found in chalk depositsin Kansas.

In 1983, a very large Argentavis fossW wasfound in Argentina. The bird would haveweighed 265 pounds (120 kg} and had a25-foGt (7.6-m) wingspan.

2 6 D I G G I N G FOR B I R D S

In 1784, the firstpterosaur wasdiscovered in alimestone bedin Solnhofen,Germany. Pterosaurremains are stillbeing found tbere.

In 1861, the first Archaeopteryxskeleton was found in limestonebeds in Germany. At first,scientists thought the find wasa pterosaui, or flying reptile, butthey were wrong. Seven fossilsand a feather have been foundin the same place.

In 2003, Chinese fossil huntersdiscovered a new species of flyingdinosaur and named it Microraptorgui. It was the size of a pigeon andhad two sets of wings on its frontand back legs. Scientists believeit used its wings to glide from treeto tree. For this reason, scientistsbelieve the Microraptor gui mghxbe the link between dinosaursand birds.

Hundreds of moa fossilswere found in a swampin New Zealand in 1937

ANTARCTICA Í311 Miles1501 Kilometers

BIRDS 27

FurtherResearch

WEB SITES

For information about different kinds of prehistoric life, including birds,visit: http://www.enchantedlearning.com

For more information about prehistoric life, visit:http://www.tyrrellmuseum.com

To find out how to become a paleontologist, visit:http://www.paleosoc.org

To find out the latest buzz in the world of paleontology, visit:http://www.ucmp.berkeley.edu/diapsids/dinobuzz.html

Arnold, Caroline. Dinosaurs with Feathers: The Ancestors of ModernBirds. New York: Clarion Books, 2001.

Matthews, Rupert. Pterodactyi. Chicago: Heinemann Library, 2003.

O'Donnell, Kerri. Birds: Modern-day Dinosaurs. New York:Rosen, 2002.

Shealy, Dennis. Dinosaurs Alive! The Dinosaur-Bird Connection.New York: Random House, 2003.

28 FURTHER RESEARCH

Ancient Activity

I magine you are a

paleontologist. Your

job is to compare

Archaeopteryx with

modern birds to see

how closely they are

related. What features

rr\2ike Archaeopteryx a

bird? What features

m2.ke Archaeopteryx a

dinosaur? Think of

as many things as

you can for each,

and then check your

answers below.

BIRDS 2 9

Quiz

Based on what you have read,answer the following questions:

1. What type of dinosaur dopaleontologists think wasthe ancestor of birds?

2. In which era didArchaeopteryx Wyel

3. Which flightless bird stood9 feet (2.7 m) high?

4. Name the flying dinosaurdiscovered by Chinese fossilhunters in 2003.

5. How were prehistoric babybirds born?

6. What two theories dopaleontologists use to explainhow birds started to fly?

7. What is the largest knownflying animal?

8. When did many birdsbecome extinct?

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30 QUIZ

Glossary

adapted: adjusted to differentconditions or environments

bipedal: an animal that walkson two legs

continent: a large land mass

distinctive: a feature thatmakes something uniqueor special

embryo: what an animal iscalled before it is born

environment: an area in whichsomething lives

evolved: changed slowlyovertime

extinct: no longer aliveanywhere on Earth

mammals: warm-bloodedanimals that give birth tc liveyoung, have hair on their bodies,and produce milk for their young

meteorite: a body of rockfrom outer space that hasreached Earth

migration: the movement fromon3 region to another for feedingor breeding

paleontologists: scientistswho study dinosaurs and otherprehistoric animals

predators: animals that catchand eat other animals for food

pray: an animal that is huntedfor food

species: a group of animalsthat are similar and canbreec together

tboory: an idea that explainsan event or fact

wisbbone: a special bonethat is the right and leftcollarbones fused together;founc only on birds

BIRDS 31

Index

Aepyornis 17,18Albertosaurus 5amber 10Andalgalornis 17Archaeopteryx 5,7, 9,10

12,17,27,29archosaurs 7Argentavis 17,20,26

carnivore 21Cenozoic Era 7Cretaceous Period 4, 8,

22,23crocodiles 9

Deinonychus 14,15Diatryma 16,19dinosaur . . . .4 ,5 ,6 ,7 ,9 ,11,14

15,18,20,23,24,27,29dodo 9,17,19,22

eggsembryo

18,19,2318

food web 21fossil 6,7,10,11,12,

18,23,26,27

Ichthyornis 23,26

Jurassic Period 4, 7, 8,17

mammals 7, 23

Mesozoic Era 6, 7, 8meteorite 22Microraptor gui 15, 27moa 17,19,20,27

neognathous 15

ornithologists 13

palaeognathus 15paleontologists 5,9,11,12

18,19,23,26,29Paleozoic Era 6Pangaea 8period 6Precambrian Era 6pterosaur 4, 5, 7, 9, 24, 27

Quezalcoatlus 5, 9,25

theropod 5,9,14,15Triassic Period 8

herbivore

32 INDEX

21 wishbone 7,12,29