what are birds classified as

Birds are classified as members of the class Aves in Linnaean taxonomy, which is the most widely accepted classification system currently in use. Phylogenetic taxonomy also places Aves in the clade Theropoda. Birds are a group of warm-blooded vertebrates characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. All birds are classified as members of the Kingdom Animalia and Phylum Chordata. Birds are not classified as reptiles, but they are more closely related to reptiles than to mammals.