Class Ave (Latin, avis = bird). Feathers and flight are the two features that distinguish birds from other vertebrates.  The two features that are common among birds and reptiles are the ability to lay amniotic eggs and presence of scale on their legs. 

Birds are lightweight animals because their bones are hollow.  A low body weight is an important feature for flight.  Structurally all birds are alike, but not all birds can fly such as penguins, ostriches, chickens, flamingos, and our thanksgiving turkeys.

Birds feed on a variety of foods (vegetation, seeds, insects, and seafood) that can be found on land or sea.