Plain-crowned Spinetail

The plain-crowned spinetail is 15 to 17 cm (5.9 to 6.7 in) long and weighs 13 to 22 g (0.46 to 0.78 oz). The sexes have the same plumage. Adults of the nominate subspecies S. g. gujanensis have a faint grayish buff supercilium on an otherwise grayish brown face. Their crown and upperparts are dull brownish that is slightly grayer and darker on the forecrown. Their wings are dark rufous with duller tips on the flight feathers. Their tail is dark rufous; it is graduated and the feathers have pointy tips. Their throat is whitish and their breast, flanks, and undertail coverts are brownish. Voice: The plain-crowned spinetail's song varies geographically. In northeastern Brazil it is "2 well-separated notes, 1st note high, sharp, explosive 'Whip', 2nd note lower 'wuh', together as 'Whip wuh' ". In western Brazil (inornata) it is " 'tjuh mcweet', 1st part slightly downslurred, 'weet' much higher". The song in Ecuador is rendered "a leisurely 'keé, kuh' repeated at several-second intervals".