Birds (Latin Aves) - a group of warm-blooded egg-laying vertebrates, traditionally considered in the rank of a separate class [K 1]. They represent a well-isolated group against the background of other modern animals, one of the most characteristic features of which is a feather cover protecting the body from unfavorable temperature changes and playing an important role in flight [1]. Ability to fly is the main feature of birds (its absence in some species is a secondary phenomenon) [2]. The forelimbs took the form of wings.