BIRDS
Birds are a
group of warm-blooded vertebrates constituting the class Aves, characterized by
feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high
metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
Birds live worldwide and range in size from the 5 cm (2 in) bee hummingbird to
the 2.75 m (9 ft) ostrich. There are about ten thousand living species, more
than half of which are passerine, or "perching" birds.
Birds have
wings whose development varies according to species; the only known groups
without wings are the extinct moa and elephant birds. Wings, which evolved from
forelimbs, gave birds the ability to fly, although further evolution has led to
the loss of flight in some birds, including ratites, penguins, and diverse
endemic island species. The digestive and respiratory systems of birds are also
uniquely adapted for flight. Some bird species of aquatic environments,
particularly seabirds and some water birds have further evolved for swimming.
Birds are
vertebrate animals adapted for flight.
Many can also
run, jump, swim, and dive. Some, like penguins, have lost the ability to fly
but retained their wings. Birds are found worldwide and in all habitats. The
largest is the nine-foot-tall ostrich. The smallest is the two-inch-long bee
hummingbird.
Kingfishers are
small birds of the order Coraciiformes. There are about 90 species, mostly in
the Old World and Australasia; most species are tropical in distribution. Their
feathers are often bright colours, such as blue or orange. They have large
heads, long, sharp bills, short legs, and stubby tails.
Kingfishers or
Alcedinidae are a family of small to medium-sized, brightly colored birds in
the order Coraciiformes. They have a cosmopolitan distribution, with most
species found in the tropical regions of Africa, Asia, and Oceania. The family
contains 114 species and is divided into three subfamilies and 19 genera.
The
black-rumped flame back, also known as the lesser golden-backed woodpecker or
lesser golden back, is a
Flamingos or
flamingoes are a type of wading bird in the family Phoenicopteridae, the only
bird family in the order Phoenicopteriformes. Four flamingo species are
distributed throughout the Americas, including the Caribbean, and two species
are native to Africa, Asia, and Europe.
The greater flamingo is the most widespread and largest species of the flamingo family. It is found in Africa, on the Indian subcontinent, in the Middle East, and in southern Europe
Parrots, also
known as psittacines, are birds of the roughly 393 species in 92 genera
comprising the order Psittaciformes, found mostly in tropical and subtropical
regions. The order is subdivided into three superfamilies: the Psittacoidea,
the Cacatuoidea, and the Strigopoidea.
Everything
about the anatomy of a bird reflects its ability to fly. The wings, for
example, are shaped to create lift. The leading edge is thicker than the back
edge, and they are covered in feathers that narrow to a point. Airplane wings
are modeled after bird wings.
The bones and
muscles of the wing are also highly specialized. The main bone, the humerus,
which is similar to the upper arm of a mammal, is hollow instead of solid. It
also connects to the bird’s air sac system, which, in turn, connects to its
lungs. The powerful flight muscles of the shoulder attach to the keel, a
special ridge of bone that runs down the center of the wide sternum, or
breastbone. The tail feathers are used for steering.
Birds have a
unique digestive system that allows them to eat when they can—usually on the
fly—and digest later. They use their beaks to grab and swallow food. Even the
way a bird reproduces is related to flight. Instead of carrying the extra
weight of developing young inside their bodies, they lay eggs and incubate them
in a nest.
The fossil
record shows that birds evolved alongside the dinosaurs during the Jurassic
period 160 million years ago. The best known fossil is archaeopteryx, which was
about the size of a crow.
