Britannica Student Encyclopedia - 2010

long and weighs less than 0.1 ounce (3

grams). The largest living bird is the

ostrich. Some male ostriches can stand 8

feet (2.5 meters) tall and weigh 300

pounds (135 kilograms).

Feather colors range from drab to very

bright. In many species the male is more

brightly colored than the female. The

female’s dull coloring may help it

remain hidden in the nest. In some

cases, the brightly colored male perches

a short distance away from the nest. In

this way, the male bird draws the attention

of enemies to himself and away

from the eggs and young. The male’s

Many people keep parakeets or

other birds as pets.

There were

no house

sparrows,

starlings, or

domestic

pigeons in

North

America

before Europeans

arrived.

Settlers

brought the

birds from

Europe.

76 Bird BRITANNICA STUDENT ENCYCLOPEDIA

 

showy coloring may also help it to

attract a mate.

Flight and Basic Structure

Most birds can fly. They are able to do

so because of their body structure and

feathers. Flying birds are strong but

light. Their powerful chest muscles help

them flap their wings. Many of their

bones are hollow, which keeps them

light. Their compact bodies narrow

toward the ends like jet airplanes. Air

flows smoothly over their feathers while

they fly.

However, a few types of bird cannot fly.

Penguins have paddlelike wings that are

useless for flying. But their wings help

them swim well. Ostriches and similar

flightless birds have small wings and

weak chests. They walk or run

everywhere on their strong legs. Most

other kinds of bird can walk (or swim)

and fly.

Every bird has two legs, two feet, and a

bill. Many birds have a pouchlike area of

the throat called the crop. The crop is

used to store food. Many birds also have

a gizzard, a part of the stomach that

grinds up food. Birds lack teeth, so they

cannot chew their food.

Feathers

Feathers help birds fly and protect them

from water, heat, and cold. Birds rearrange

and clean their feathers regularly.

Most kinds also apply oil to the feathers

from a gland near the tail.Water slides

off the oiled feathers instead of soaking

through. At least once a year birds shed

Birds have different kinds of bills to help

them eat different kinds of food.

BRITANNICA STUDENT ENCYCLOPEDIA Bird 77

 

their old feathers and grow new ones.

This process is called molting.

Senses

Birds have sharp eyesight. For instance,

an American kestrel flying 100 feet (30

meters) above a field can spot a

grasshopper on the ground below.

However, birds generally have a

narrower range of hearing than humans

do. Their sense of smell is usually not

highly developed.

Behavior and Feeding Habits

Some types of bird live alone most of the

time. Other types are more social. They

may feed, sleep, fly, and nest in groups

called flocks.

Birds use many different sounds to communicate

with one another. For

example, some baby chicks stop moving

when their mother produces a danger

call. Birds may sing to attract mates.

They may also sing to announce that a

certain patch of land belongs to them.

Birds eat a wide variety of foods. Many

types eat insects. Some waterbirds catch

fish. Birds of prey catch many kinds of

animals, including other birds. Some

birds, such as vultures, feed on dead

animals and garbage. Many other types

eat plant material, such as seeds and

fruits.

Reproduction

Most birds breed at least once a year.

Many types build nests for their eggs. A

nest can range from a scrape in the sand

to a cup of twigs and mud to a complex

hanging basket. The female bird lays a

set of anywhere from 1 to 20 eggs,

depending on the species.

Most birds sit on their eggs to keep

them warm. This process is called incubation.

The eggs hatch into young birds

in about 11 to 80 days, depending on

the species. Some young birds can feed

themselves almost immediately. Other

types depend on their parents to provide

their food for a time.

#More to explore

Animal • Dinosaur • Feather

• Migration, Animal • Pet • Poultry

Bird, Flightless

Millions of years ago, all birds could fly.

But as time passed, some birds became

flightless. That is, they lost the ability to

fly, though they still have wings.

An American robin brings a worm to its

hungry young.

78 Bird, Flightless BRITANNICA STUDENT ENCYCLOPEDIA

 

Why Some Birds Do Not Fly

Scientists do not agree on how some

birds became flightless. One idea has to

do with where the birds lived. The first

flightless birds may have appeared in

isolated places, or places cut off from the

rest of the world. Birds living in these

isolated spots, like islands, found no

enemies. For that reason, they did not

need to fly to stay alive. So, as these

birds evolved, or developed over thousands

of years, they gradually lost their

ability to fly.

Flightless Birds Today

The largest flightless birds are the

ostriches of Africa. Rheas, emus, and

cassowaries are other large flightless

birds. Rheas live in South America,

emus live in Australia, and cassowaries

live in Australia and New Guinea. All

these birds are about 5 feet (1.5 meters)

tall and have very strong legs.

Kiwis and penguins are two kinds of

smaller flightless birds. Kiwis are about

the size of a chicken. They live in New