Birds (Latin Aves) - Class feathered, warm-blooded, egg-laying vertebrates, whose front legs are in the shape of the wings. Initially, the structure of birds adapted to flight, although at present there are many species of flightless birds. Another distinctive feature of birds is the presence of the beak. Today on earth there are more than 9,800 different species, making them the most diverse group of superclass tetrapods.
Birds spread on all continents and in all ecosystems from the Arctic to the Antarctic. The smallest member of this class is considered to be living on Cuba and the Isla de la Juventud, the bee hummingbird (Mellisuga helenae) - the length of her male does not exceed 5.7 cm, and the largest one is African ostrich (Struthio camelus) in height to 270 cm.