A medium-sized, fairly small bird of lowland and foothill forest interior. Black upperparts, head and marks on the sides of the chest, underparts white up to the bill, thin white eye-brow, wedge below the eye and patch in the wing. Shy and difficult to see. Very similar to Black- chinned Robin and co-occurs in some areas, but Black-sided has black on the sides of the chest, and has a narrower white eyebrow. Heard more often than seen. Voice, a distinctive “wee-chow!”, the second note with an explosive quality.