Ash-browed Spinetail

The ash-browed spinetail is 14 to 15 cm (5.5 to 5.9 in) long and weighs 14 to 21 g (0.49 to 0.74 oz). The sexes have the same plumage. Adults of the nominate subspecies have a supercilium that varies from bold whitish to obscure dingy gray. The rest of their face is dull brownish with some pale streaks on the ear coverts. Their forehead is brown with some reddish chestnut, their crown reddish chestnut, and their back rich brown that becomes increasingly reddish by the uppertail coverts. Their wings are reddish chestnut; their flight feathers are slightly paler with dark fuscous tips. Voice: The ash-browed spinetail's song has variously been described as "a high-pitched, accelerating, descending and fading series of shrill notes with bouncing-ball rhythm", a "fast, accelerating, but fading trill", and "a fast and sprightly series of shrill notes that usually ends in a trill and fades in intensity".