Small tyrannulet with weak yellow wingbars. Olive yellow, with a grayish head, thin whitish yellow eyering, and dark eye. Weakly marked overall; its orange lower mandible is a good field mark. Found in the midstory and canopy of montane forest in a fairly narrow band in the foothills of the Andes, roughly 500-1400 m in elevation. Sometimes joins mixed-species flocks. Listen for its thin, sputtering trill that rises slightly; buzzier and softer than other bristle-tyrants.