File:Sialia currucoides (mountain bluebird) (western North Dakota badlands, USA) 1.jpg

English: Sialia currucoides (Bechstein, 1798) - female mountain bluebird in the western North Dakota badlands, USA. (photo by Mary Ellen St. John)

Classification: Animalia, Chordata, Vertebrata, Aves, Passeriformes, Turdidae

---

Birds are small to large, warm-blooded, egg-laying, feathered, bipedal vertebrates capable of powered flight (although some are secondarily flightless). Many scientists characterize birds as dinosaurs, but this is consequence of the physical structure of evolutionary diagrams. Birds aren’t dinosaurs. They’re birds. The logic & rationale that some use to justify statements such as “birds are dinosaurs” is the same logic & rationale that results in saying “vertebrates are echinoderms”. Well, no one says the latter. No one should say the former, either.

However, birds are evolutionarily derived from theropod dinosaurs. Birds first appeared in the Triassic or Jurassic, depending on which avian paleontologist you ask. They inhabit a wide variety of terrestrial and surface marine environments, and exhibit considerable variation in behaviors and diets.