Nest parasite that lays its eggs in the nests of African Firefinch. Breeding males are glossy blue-black, with a pale brownish panel in the wings, while females and non-breeding males are streaky and brown on the back and pale below, with a bold facial pattern. The color of the legs is red in South Africa and pale pink in the rest of the range. Found in savanna, woodland, and forest edge. Mimics the vocalizations of its host firefinches: a low metallic trill. Extremely similar to several localized indigobirds and the widespread Purple Indigobird. In South Africa, separated from Purple Indigobird by red legs. Elsewhere, breeding males are probably slightly less glossy but only separated with certainty by hearing mimicked vocalizations of host species.