Presented by the
Ornithological Council

Member organizations of the Ornithological Council

American Ornithologists' Union

Association of Field Ornithologists


Cooper Ornithological Society

Neotropical Ornithological Society

Pacific Seabird Group

Raptor Research Foundation

Society of Canadian Ornithologists ~ Société des Ornithologistes du Canada

Society for the Conservation and Study of Caribbean Birds

The Waterbird Society

Wilson Ornithological Society
Page Last Updated
Wed, Dec 29, 2010

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What is a bird?


Two-legged, bipedal vertebrates, distinguished from other living vertebrates by feathers. All birds have bills, and they have a 4-chambered heart.

   ~ after Gill, F. B. 1995. Ornithology
      Second edition. Freeman, New York

  Galápagos Mockingbird, Nesomimus parvulus
Galápagos Mockingbird
Mimus parvulus


Kingdom: Animalia (animals)
Phylum: Chordata (animals with a spinal chord)
Subphylum: Vertebrata (animals with a backbone)
Class: Aves (living and extinct birds)

Closest relatives

Living: crocodiles & alligators

Extinct: theropod dinosaurs (probably) or crocodilians and dinosaurs together (alternative hypothesis, which envisions a common ancestor for birds, crocodilians, and dinosaurs, probably in the late Permian or early Triassic Period)

We now know that some dinosaurs had feathers, as explained at these sites:
 National Geographic Society
 Australian Museum online