Small yellow warbler found in the understory of Andean forest and scrub from around 2,500-3,500m. Olive above and brighter yellow below, with bright yellow eyebrow and black crown. Sexes similar. Compare with Citrine Warbler, which does not show a black crown. Fairly common. Pairs forage low, often among mixed-species flocks, where they can be difficult to spot among the dense scrub and bamboo. Frequently detected by accelerating series of musical chips.