All birds have feathers, and feathers are peculiar to birds. No other major group of animals is easy to categorize. All birds have wings, too, but there are other winged creatures, such as bats and certain insects.
Many adaptations are found in both feathers and wings. Feathers form the soft down of goose and ducks, the showy plumes of ostriches and egrets, and the strong flight feathers of eagles and condors.Wings vary from the short, broad ones of chickens, which seldom fly, to the long, slim ones of albatrosses, which spend almost all their lives soaring on air currents. In penguins, wings have been modified into flippers and feathers into a waterproof covering. In kiwis, the wings are almost impossible to detect.
Yet diversity among birds is not as striking as it is among mammals. The difference between a hummingbird and an emu is great, but hardly as dramatic as that between a bat and a whale. It is variations in details rather than in fundamental patterns that have been important in the adaptation of birds to many kinds of ecosystems.
All birds have feathers, and feathers are peculiar to birds. No other major group of animals is easy to categorize. All birds have wings, too, but there are other winged creatures, such as bats and certain insects.Many adaptations are found in both feathers and wings. Feathers form the soft down of goose and ducks, the showy plumes of ostriches and egrets, and the strong flight feathers of eagles and condors.Wings vary from the short, broad ones of chickens, which seldom fly, to the long, slim ones of albatrosses, which spend almost all their lives soaring on air currents. In penguins, wings have been modified into flippers and feathers into a waterproof covering. In kiwis, the wings are almost impossible to detect.Yet diversity among birds is not as striking as it is among mammals. The difference between a hummingbird and an emu is great, but hardly as dramatic as that between a bat and a whale. It is variations in details rather than in fundamental patterns that have been important in the adaptation of birds to many kinds of ecosystems.
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