Each of the monotypic groups is recognized as a separate species: the group Vieillot's Weaver (Chestnut-and-black) Ploceus nigerrimus castaneofuscus becomes Chestnut-and-black Weaver Ploceus castaneofuscus; and the group Vieillot's Weaver (Black) Ploceus nigerrimus nigerrimus becomes Vieillot's Black Weaver Ploceus nigerrimus. Plumages of the two species are quite distinct, in both sexes (del Hoyo and Collar 2016). The ranges of Chestnut-and-black Weaver and Vieillot's Black Weaver abut, a contact zone that has not been studied in detail, but any hybrid zone, if present, apparently would be quite narrow in comparison to the widespread distributions of the two species.