The Glittering-bellied Emerald is one of the most broadly distributed of southern South American hummingbirds, although it is unknown from Chile. From central Bolivia and E Brazil it ranges south to Uruguay and NC Argentina; it is the southernmost of the hummingbirds found in the eastern lowlands of southern South America. This is also the southernmost representative of a genus with many species; a classic feature of this genus is the orange-red bill with a dark tip. The Glittering-bellied Emerald is entirely shiny green throughout, although the throat and mid-belly are blue. As is typical the bill is orange-red with a dark tip. Males have an iridescent blue tail that is noticeably forked. Females are entirely different, showing green upperparts and off white to pale grayish underparts. Most distinctive is that the face is dark (sooty grey) and is outlined above by a white supercilium which curls down towards the neck sides, in the field it gives the impression of looking masked. As in the male, the bill is orange at the base and dark at the tip, although the orange is duller and more restricted. The tail of the female is broadly tipped white on the outer two rectrices, unlike that of the males; this is a typical pattern in many hummingbirds that the tail shape and pattern is often radically different between males and females. Females have a notched, rather than forked tail, but as in the males it shows a blue iridescence.