The Torrent Tyrannulet is a small, distinctive flycatcher that lives along fast-moving mountain streams from Costa Rica south to northern Bolivia. This species often perches on rocks or low branches in or close to the edge of streams where it forages by making short flights or gleaning rocks to capture insects (not snakes, as implied by the etymology of the name of the genus). The flight of this species is low, direct, and fast. Torrent Tyrannulet is bold and conspicuous, and is generally easy to see where it occurs. The genus Serpophaga shows a distinctive shape and posture for a flycatcher, with sturdy legs, a pot-belly, a large head, and a medium length tail that is often held cocked. The body plumage of Torrent Tyrannulet is mostly pale gray, with a paler belly and a whitish throat, with a dark slaty cap that extends down below the eye, as well as blackish wings and tail.