Birds of the World

Birds form the class Aves, a group of feathered, warm-blooded vertebrates distinguished by toothless beaked jaws, the laying of hard-shelled eggs, and, in most species, the ability to fly. Their bodies are highly adapted for flight: lightweight bones, powerful chest muscles and feathered wings allow many to travel great distances, while feathers also provide insulation and waterproofing. Birds descend from theropod dinosaurs, a relationship supported by an extensive fossil record, and today number roughly ten thousand living species.

Birds occupy almost every habitat, from open ocean to mountain forest, and their beaks and feet reflect their diets and lifestyles. A falcon, for example, has a hooked bill and sharp talons suited to hunting, while wading and dabbling species such as the blue duck are shaped for life in or near water. Some birds, including the kiwi and the kakapo of New Zealand, are flightless, having evolved on islands historically free of ground predators. The kakapo is a heavy, nocturnal, ground-dwelling parrot, while the brown, great spotted and little spotted kiwis are nocturnal probers of the forest floor.

New Zealand illustrates how isolation produces distinctive birdlife. Its native species include the weka, the alpine parrot known as the kea, several parakeets, the morepork owl, the tiny rifleman, the bush wren, the brown creeper and the grey warbler, along with cuckoos such as the shining and long-tailed cuckoo. Many island birds are now threatened by introduced mammals, making them a focus of conservation work.

Frequently asked questions

What makes birds different from other animals?

Birds are the only living animals with feathers. They also have beaks without teeth, lay hard-shelled eggs, and most can fly.

Why are some birds flightless?

Flightless birds such as the kiwi and kakapo often evolved on islands without ground predators, where flight gave little advantage and was eventually lost.

What class do birds belong to?

Birds belong to the class Aves, a group of warm-blooded vertebrates that descended from feathered dinosaurs.