Birds are a group of warm-blooded vertebrate animals constituting the class Aves, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chamb
Archaeopteryx is often considered the oldest known true bird.
Anchiornis huxleyi is an important source of information on the early evolution of birds in the Late Jurassic period.
Confuciusornis sanctus, a Cretaceous bird from China that lived 125 million years ago, is the oldest known bird to have a beak.
The range of the house sparrow has expanded dramatically due to human activities.