Small, compact brown warbler with distinct black streaking all over the body. Note evenly spaced narrow pale fringes to the tertials in adults and juveniles. Very hard to see when not singing, but when located can be very confiding. Breeds in swampy open forests, reedbeds, and swampy edges across the taiga; winters in similarly tangled and densely vegetated habitat. Song is a long insectlike trill which ascends then descends as the bird moves its head; can be difficult to pin down. Calls from cover, giving a dry, incessant “chit-chit-chit-chit”.