Resembles Sedge Warbler, but larger with a thick and well-marked white eyebrow and throat; contrasting dark cap; rufous rump, nape, and sides; short wings; and dark legs (pale in Sedge). Found in dense reed beds, often with bulrush stands. Makes muffled "treck" calls recalling a stonechat. Scratchy, repetitive song is given from the upper half of a plant stalk; does not sing in flight.