A rare, small bird of mid-montane forest understory. As the name suggests, just 2 colors. Blackish upperparts and rufous underparts. Moves in small groups, foraging for insects on the forest floor. Similar to Rusty Mouse-Warbler, but Bicolored is usually found higher and has a rufous rather than white throat. Call, an excited chattering. Song, a series of clear, whistled notes, either ascending or descending.