A very secretive warbler that keeps deep in cover. Overall it appears dark grey-brown, with bold black streaking across the back and long undertail coverts marked by large dark centres. It prefers damp, overgrown habitats such as grassy thickets, heaths, and rank scrub, often close to water. Rarely seen unless in song, it typically sings from a perch in tall grass or a low bush, most often late in the day and sometimes after dark. The song is a long, insect-like reeling trill, and it gives a sharp, high “pik” call.