Mid-sized, long-billed warbler with rich yellow underparts and an olive-green back. The color of the cap varies geographically. In some subspecies, it is black, while in others, it is olive-green like the back. Found in wet scrub, often adjacent to wetlands. Generally skulks in thick undergrowth. Distinctive song is a couple of quick introductory chips followed by a vibrating trill. Other yellow-warblers are similar, but have a paler cap and are found in different habitats.