There are currently over 9000 bird species. They differ in their origin, lifestyle and features of the external and internal structure. All birds are divided into three groups: penguins, ostriches and typical flying birds.
Penguins are flightless birds, but they swim and dive very well. The penguins’ small wings have turned into flippers. The body of these birds is dense, covered with thick feathers. They have a flexible neck and a sharp beak. Usually penguins have a black back and a white belly. They move vertically on land, leaning on the tail. Penguins live mainly in the colder regions of the Southern Hemisphere.
Ostrich birds include flightless African ostriches, American rheas, Australian cassowaries, emu and kiwi. A feature of these birds is the structure of the sternum: it is flat and without a keel. The forelimbs (wings) in ostriches are poorly developed. The hindquarters are long and strong, adapted for fast running.
Among the typical flying birds, about 40 orders are distinguished.
The order of passerines is the most numerous of them. It includes more than 5 thousand species, including various species of larks, sparrows, swallows, wagtails, starlings, crows, magpies, and blackbirds. Most passerines live in forests. The legs of the birds of this order are four-toed (three toes are directed forward and one is directed backward). During the nesting period, they live in pairs, skillfully build nests. Chicks are born naked, helpless.
Of the other orders of birds, the largest in terms of the number of species are Charadriiformes, Anseriformes, Chicken-like, Falconiformes, Stork-like, Dove-like.
The order of Charadriiformes (woodcock, lapwing, plover, carrier and other waders) are small and medium-sized birds with long legs and a thin, long beak. They live in wetlands, along the banks of rivers and other bodies of water. They feed mainly on invertebrates. Sandpipers are brood birds.
A detachment of anseriformes (geese, ducks, swans). These waterfowl dive well, getting food in the water or at the bottom of the reservoir. They have dense plumage with developed down, large coccygeal gland, swimming membranes between the toes.
The order of storks, or ankles (cranes, storks, herons, bitterns), unites birds of medium and large sizes, with a long neck and long legs. They feed on damp meadows, swamps or in the coastal parts of water bodies by amphibians, small fish, and molluscs. Storks usually nest in colonies.
The group of chickens (hazel grouse, black grouse, capercaillie, quail, partridge, pheasants, wild bank and domestic chickens, turkeys) unites birds with strong legs adapted to raking the soil or forest litter when foraging, short and wide wings, providing a rapid takeoff and short flight. Gens are brood birds. Chicks feed mainly on insects, worms and other invertebrates, adults are herbivorous.
Of the pigeon-like order, the most widespread are wood pigeon, common and great turtledoves, dove, and clintuch. Pigeons are granivorous birds (they feed on seeds of various plants and feed their chicks with them). In the nesting period, they live in pairs. The rest of the time they usually keep in small flocks.
The detachment of falcon-like, or daytime birds of prey, includes falcons, hawks, kites, eagles and other birds that have strong legs with sharp curved claws, a crocheted beak, and sharp eyesight. The wings of falconifers are either narrow, sharp, facilitating fast flight, or wide, allowing them to float in the air in search of prey. The chicks of these birds hatch sighted, covered with thick down.
The group of woodpeckers includes great and lesser spotted woodpeckers, green woodpeckers, black woodpeckers, or yellow woodpeckers. Woodpeckers have a sharp, chisel-like beak, a long, sharp tongue with jagged edges, elastic ends of the tail feathers bent towards the support, legs with two toes pointing forward and two backward, and other features that distinguish birds that feed on tree trunks … The exception is the whirligig, which has a straight and weak beak, the rods of the tail are not elastic. Unlike other woodpeckers, the wormhole is a migratory bird.
Of the birds of the swift order, the black and white-backed swifts are widespread. Outwardly and in the way of feeding, they are similar to swallows.