Black-bellied thorntail

The black-bellied thorntail (Discosura langsdorffi) is a species of hummingbird in the "coquettes", tribe Lesbiini of subfamily Lesbiinae. It is found in Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela.

The black-bellied thorntail weighs about 3.2 g (0.11 oz). Males are 12 to 13.7 cm (4.7 to 5.4 in) long and females 7.4 to 7.6 cm (2.9 to 3.0 in). Adults of both sexes of the nominate subspecies have an iridescent emerald green crown and coppery green upperparts with a white band across the rump. The male's gorget is iridescent emerald green with a golden coppery band below it. Its flanks are bronzy green and the rest of the underparts black. The tail inner feathers of the tail are steely blue and the outer three pairs gray; all have white shafts. The tail is deeply forked, and the outer feathers are very narrow which give the species its common name. The female's throat is white with green and black spangles and it has a thin white streak on the cheek. Its breast is spangled green with a coppery lower border; the belly is black with a white patch on the flank. Its tail is short, only slightly forked, and steely blue with bronze at the base and white tips. Juveniles are similar to the adult female. Subspecies D. l. melanosternon is slightly smaller than the nominate; its crown is grass green, the breast more golden, and the rest of the underparts darker.