Rather long-tailed antbird of humid forest understory in lowlands as well as mountains. Male is black; female shows remarkable plumage variation throughout the large range. Her back is always brown, and most races have brown or buff head and underparts. In central Peru, female has black head and in some places also entirely black underparts. In southern Peru, female has white eyebrows. Both sexes have ruby-red eyes and a white patch on the back that is usually hidden; it is exposed when the bird is excited such as when defending its territory. Song is a very fast series of short whistles.