Birds make up the class aves. There are more than 9,000 species, almost all of which can fly (the only flightless birds are penguins, ostriches, rheas, cassowaries, and kiwis). The ability to fly is reflected in the typical bird features: forelimbs modified as wings; a streamlined body; and hollow bones to reduce weight. All birds lay hard-shelled eggs, which the parents incubate. Birds’ beaks and feet vary according to diet and way of life. Beaks range from general-purpose types suitable for a mixed diet (those of thrushes, for example), to types specialized for particular foods (such as the large, curved, sieving beaks of flamingos). Feet range from the webbed “paddles” of ducks, to the talons of birds of prey. Plumage also varies widely, and in many species the male is brightly colored for courtship display whereas the female is drab.
Birds make up the class aves. There are more than 9,000 species, almost all of which can fly (the only flightless birds are penguins, ostriches, rheas, cassowaries, and kiwis). The ability to fly is reflected in the typical bird features: forelimbs modified as wings; a streamlined body; and hollow bones to reduce weight. All birds lay hard-shelled eggs, which the parents incubate. Birds’ beaks and feet vary according to diet and way of life. Beaks range from general-purpose types suitable for a mixed diet (those of thrushes, for example), to types specialized for particular foods (such as the large, curved, sieving beaks of flamingos). Feet range from the webbed “paddles” of ducks, to the talons of birds of prey. Plumage also varies widely, and in many species the male is brightly colored for courtship display whereas the female is drab.
