hummingbird, common name for members of the family Trochilidae, small, strictly New World birds, related to the swifts, and found chiefly in the mountains of South America. Hummingbirds vary in size from a 21/4-in. (6-cm) fairy hummingbird of Cuba (the smallest of all birds) to an 81/2-in. (21.6-cm) giant hummer of the Andes, Patagona gigas. Their colors are brilliant and jewellike; the feathers have a prismatic construction that iridesces in changing light. Hummingbirds feed on insects and the nectar of flowers, for which their long, slender (sometimes curved) bills are especially adapted. They are usually seen hovering or darting (at speeds of up to 60 mi/97 km per hr) in the air as they feed in flight; their weak feet cannot support them on flat surfaces. Their wingbeats are so rapid (50–75 beats per sec) that the wings appear blurred. The enormous amount of energy expended on this continuous movement is supported by constant feeding; at night they lapse into a state of torpor like that of animals in hibernation. The nests vary but are usually tiny cups of soft vegetation fastened to the top of a branch. Several species are found in the W and SW United States, e.g., the black-chinned hummingbird and the calliope hummingbird, the smallest (3 in./7.6 cm) of the U.S. species. The only species found in the NE United States is the ruby-throated hummingbird, Archilochus colubris. The male is metallic green above and whitish below, with an iridescent ruby-red throat; the female is dull-colored. The sunbirds, small and brilliant passerine birds of India, Africa, and Australia, are sometimes called hummingbirds in those areas but belong to a different taxonomic order (Passeriformes). Hummingbirds are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Apodiformes, family Trochilidae.