birds Jump to navigation Jump to search For other uses, see Bird (disambiguation) and Birds (disambiguation) . "Aves" and "Avifauna" redirect here. For other uses, see Aves (disambiguation) and Avifauna (disambiguation) . Birds Temporal range: Early Cretaceous ( Aptian ) – Present , [1] 121–0 Mya PreЄ Є O S D C P T J K Pg N Scientific classification Kingdom: Animalia Phylum: Chordata Clade : Sauropsida Clade : Avemetatarsalia Clade : Ornithurae Class: Aves Linnaeus , 1758 [2] Extant orders and temporal range show See orders Synonyms Neornithes Gadow, 1883 Birds are a group of warm-blooded vertebrates constituting the class Aves , 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 . Birds live worldwide and range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich . There are about ten thousand
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