Mouse-colored Thistletail

The mouse-colored thistletail is 18 to 21 cm (7.1 to 8.3 in) long and weighs 15.5 to 19 g (0.55 to 0.67 oz). The sexes have the same plumage. Adults have a faint light gray-brown supercilium and a white eyering on an otherwise gray face. Their crown, back, rump, wings, and tail are dull olive-brown. Their tail is long and deeply forked with few barbs at the feather ends that give a ragged appearance. Their throat is pale gray or grayish brown (often with faint white streaks on the chin) and the rest of their underparts are pale grayish brown. Voice: The mouse-colored thistletail's song has been described as "a trill increasing in speed and amplitude, and slightly descending in pitch, lasting c. 2 s and repeated every 6 s kee kee-keekeekrkrrr...rrrrrr". Another source describes it as "a series of notes that accelerates into a trill, the first notes inflected 'sweeí, sweeí, sweeí, swi, ti-ti-titi-trrrrr' ".