|
animal with feathers
and wings. Birds are the only animals with
feathers, although some other animals, such
as insects and bats, also have wings. Nearly
all birds can fly, and even flightless birds,
such as ostriches and penguins, evolved
from flying ancestors.
|
Birds are members of a group of animals
called vertebrates, which possess
a spinal column or backbone. Other
vertebrates are fish, amphibians,
reptiles, and mammals. Many characteristics
and behaviors of birds are distinct
from all other animals, but there
are some similarities. Like mammals,
birds have four-chambered hearts and
are warm-blooded-having a relatively
constant body temperature that enables
them to live in a wide variety of
environments. Like reptiles, birds
develop from embryos in eggs outside
of the mother's body.
Birds are found worldwide
in many habitats. They can fly over
some of the highest mountains on earth
as well as both of the earth's poles,
dive through water to depths of more
than 250 m (850 ft), and occupy habitats
with the most extreme climates on
the planet, including arctic tundra
and the Sahara Desert. Certain kinds
of seabirds are commonly seen over
the open ocean thoUKnds of kilometers
from the nearest land, but all birds
must come ashore to raise their young.
|
Eclectus
parrots
cages UK |
|
|
Highly developed animals,
birds are sensitive and responsive, colorful
and graceful, with habits that excite interest
and inquiry. People have long been fascinated
by birds, in part because birds are found
in great abundance and variety in the same
habitats in which humans thrive. And like
people, most species of birds are active
during daylight hours. Humans find inspiration
in birds' capacity for flight and in their
musical calls. Humans also find birds useful-their
flesh and eggs for food, their feathers
for warmth, and their companionship. Perhaps
a key basis for our rapport with birds is
the similarity of our sensory worlds: Both
birds and humans rely more heavily on hearing
and color vision than on smell. Birds are
useful indicators of the quality of the
environment, because the health of bird
populations mirrors the health of our environment.
The rapid decline in bird populations and
the accelerating extinction rates of birds
in the world's forests, grasslands, wetlands,
and islands are therefore reasons for great
concern.
|