The blue-tailed emerald (Chlorostilbon mellisugus ) is a hummingbird found in tropical and subtropical South America east of the Andes from Colombia east to the Guianas and Trinidad, and south to northern Bolivia and central Brazil.
The blue-tailed emerald is 7.5 cm (3 in) long and weighs 2.6 g. The black bill is relatively short and straight. The male has a brilliant green plumage, with white thighs and a dark metallic blue tail (clearly forked in the northern part of its range; slightly so in the central and southern part). The female average smaller than the male and also differ by the grey-white underparts, a blackish ear patch, a short white supercilium/post-ocular streak and white-tipped outer tail feathers. The song is a pleasant twittering, and the call of this species is a pebbly tsip.
The female lays her eggs in a small cup nest, similar to that of the ruby-topaz hummingbird, placed on a horizontal tree branch. Incubation is 13 days with a further 18 days to fledging.
Blue-tailed emeralds feed on insects and nectar.
