Torrent Tyrannulet

The torrent tyrannulet is 9.5 to 12 cm (3.7 to 4.7 in) long; eight individuals weighed an average of 8.3 g (0.29 oz). Adults of the nominate subspecies have a mostly black head with a partially hidden white patch in the center of the crown. Their back, rump, and uppertail coverts are gray. Their wings are mostly black with gray or grayish white edges on the coverts. Their tail is black and sometimes has indistinct grayish white tips on the feathers. Their chin and throat are grayish white. The center of their breast and their belly are white and their undertail coverts slightly grayish. Adult females have a slightly duller black crown and nape than males and a smaller white crown patch or none at all. Juveniles have a dusky crown with some dull gray mixed in and brownish gray upperparts that are darker on the uppertail coverts. Subspecies S. c. grisea is smaller and paler than the nominate and has less white in its crown. Both sexes of both subspecies have a dark brown iris, a black bill, and black legs and feet.

The torrent tyrannulet has a disjunct distribution. Subspecies S. c. grisea is the more northern of the two. It is found from the Cordillera de Tilarán in southern Alajuela Province of Costa Rica south to western Panama's Veraguas Province. The nominate subspecies is found in the Andes of Venezuela's Trujillo, Mérida, and Táchira states, in the Serranía del Perijá that straddles the Colombia-Venezuela border, in northern Colombia's isolated Sierra Nevada de Santa Marta, along all three chains of the Colombian Andes, and south through central Ecuador and central Peru into western Santa Cruz Department in Bolivia. There are also isolated populations in west-central Peru. The torrent tyrannulet is a bird of rocky fast-flowing mountain streams, primarily in the highlands and less often at lower elevations where the water flows slower. It favors relatively small watercourses in forested terrain though it also occurs on streams in more open landscapes and occasionally in marshes and flooded forest. In elevation it ranges in Costa Rica mostly between 500 and 2,200 m (1,600 and 7,200 ft) and occasionally lower on the Caribbean side. …

The torrent tyrannulet feeds on arthropods, primarily flying insects. It forages actively, singly or in pairs, and primarily by hawking during a short flight from boulders in the stream. Between flights it characteristically wags and flicks its tail. It also takes prey from streamside vegetation while perched in it or briefly hovering, and has been observed feeding on the ground in grassy areas and on gravel paths.