Birds (lat. Aves) – a class of warm-blooded egg-laying vertebrates. Are well-isolated group, one of the most characteristic features of Representatives which is the covering of feathers that protects the body from adverse changes in temperature and plays an important role in flight. The ability to fly is the main feature of birds (the absence of such capacity in some modern birds – a secondary phenomenon). Upper limbs acquired shape of the wings. Birds have a special structure of the respiratory system and the digestive system, which is closely linked to their ability to fly. Another distinguishing feature is the presence of the beak.
Many species of birds make regular long migrations from one region of the earth to the other. More more nomadic, constantly moving over short distances within the area. Birds are social animals, communicating with each other by means of visual and acoustic signals, and in some cases fulfilling social action: communal nesting, joint hunting and protection from predators. For most species are characterized by monogamy. Typically, eggs are laid in a nest and incubated by both members of the pair. Most birds for a long time caring for their offspring after birth.
Birds inhabit all the ecosystems of the Earth, including the internal parts of Antarctica. According to the International Ornithological Congress on February 2015 science knows 10,560 living species of birds (20,811 subspecies), as well as 149 species extinct in modern historical time. This makes it the most diverse group of birds superclass quadrupeds. On the territory of Russia noted 789 species, including 657 nesting species; 125 species of nesting are not shown, and 7 of extinct species.
As the most abundant and widely distributed class of higher vertebrates, and also due to the nature of their biology birds play an important role in nature and human life. Many species are of economic importance. Poultry farming is one of the main branches of agriculture producing for human meat, eggs and fat, as well as feathers. Many species of birds contain as pets. Due to human activities, many birds got their further development, some steel Sinanthropus, but at the same time, about 1,200 species in varying degrees, are at risk of extinction and are protected by national and international legislation.