Eastern Dwarf Hornbill Horizocerus granti is split from Black Dwarf (now Western Dwarf) Hornbill H. hartlaubi (Clements 2007:229)

Summary: The Congo River separates two very distinct forms of Black Dwarf Hornbill, now recognized as separate species, Eastern and Western Dwarf Hornbill.

Details: Horizocerus granti was originally described as a distinct species by Hartert (1895), but has long been treated as a subspecies of the Black Dwarf Hornbill H. hartlaubi (e.g., Peters 1945). The several morphological differences between these taxa (e.g., Hartert 1895, del Hoyo and Collar 2014) appear consistent with a parapatric distribution across the Congo River. Thus, WGAC and Clements et al. (2023) agrees with the HBW and BirdLife International (2022) treatment of H. granti as specifically distinct.

English names: The English names Western Dwarf Hornbill H. hartlaubi and Eastern Dwarf Hornbill H. granti are used as these combine more familiar elements of the name with geographic descriptors than do the names used in HBW and BirdLife International (2022).