The narrow, forked tails of these small-bodied hummingbirds is over twice the length of their bodies. Males and females are bright green and females are white below with extensive green spotting. Green-tailed Trainbearers inhabit second growth, shrubby forest edges, bush-filled pastures, parks, páramo, and areas with hedges. At higher elevations, they are typically outcompeted by the larger Black tailed Trainbearer (Lesbia victoriae). Active and defensive, these hummingbirds weave around, hovering at flowers at various heights, and females hold small floral territories. During courtship displays, individuals make snapping sounds with their tails.