Small, strikingly-plumaged antbird with a long tail and a very restricted range. Inhabits the understory of low stature or regenerating forests, forest edges, scrub, and abandoned plantations where it is very active and occasionally joins mixed-species flocks. Much plumage variation, with coastal males near Rio de Janeiro (formerly split as Restinga Antwren) being almost uniformly sooty-black with only slightly grayer back and spotted white wingbars. Two more northerly subspecies vary between rufous-brown and dark gray above, but both are black below with a bold white eyebrow and white wing spots. In all subspecies, females are pale whitish below and brown above with a bold white eyebrow. Male song is a monotonous series of harsh chip notes; female gives nasal squeaks.