Ranging across much of northern South America, including western Brazil and south into Bolivia, the Blue-tailed Emerald is found in fairly open and semi-dry habitats in the tropical and subtropical zones, (up to 2200m). It is widespread and common in Colombia and Venezuela, fairly common in the Guianas, and uncommon to local in Ecuador and Trinidad. Males are almost entirely emerald green, with white thighs, and blue hues sometimes visible in the face and breast. The bill is straight and black, and the dark, iridescent blue tail is forked, resting nearly even with the primaries when perched. Females are a lighter green above with gray underparts and limited green flanks. Dark auriculars between a white post-ocular stripe and the pale throat lend them a vaguely masked appearance. Females’ tails are less forked and pale-tipped. It often perches at low levels and forages with quick and direct flights to flowering trees or shrubs, and nectar piracy has also been observed.