A dull warbler restricted to Sulawesi with a pale eyebrow, a largely blackish bill, dark legs, dingy olive-brown upperparts, and a pale yellow underside. No distinct wingbar. Two forms: southwestern form shows a central crown stripe that is faint or absent farther north; a more extensive pale base to lower section of bill; and a paler underside. Found in forests and edges in hills and mountains, often accompanying mixed-species flocks. Differs from Arctic, Japanese, and Kamchatka Leaf Warblers in darker brown coloration, dull legs, yellow underside, and lack of distinct wingbar. Song is a highly variable mix of warbles and trills.