Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. This category contains taxa at the order or higher level in the class of Aves.

Unlike Category:Prehistoric birds, which covers all prehistoric avialans, even non-neornithines, this category only covers neornithines. Category:Prehistoric birds is therefore not a descendant of Category:Birds.

For individual species of birds, see the subcategories, particularly category:Birds by classification and category:Birds by country.