Trainbearers are lopsided hummingbirds: they have short bills (for a hummingbird, anyway), but very long tails. The Black-tailed Trainbearer occurs from Colombia south to Peru. Over much of its range it overlaps with a related species, the Green-tailed Trainbearer (Lesbia nuna), but the Black-tailed is the larger of the two species, with a longer bill. The two species also differ in the color of the upper surface of the tail: the tail feathers of Black-tailed are mostly black, with only narrow glittering bluish green tips, but are mostly green in the smaller species. Unlike the superficially similar sylphs (Aglaiocercus), trainbearers are not hummingbirds of the forest. Instead, the Black-tailed Trainbearer forages in montane scrub, in gardens, and other semiopen habitats.