Crested Guineafowl is split into three species, based on differences in the color and pattern of the bare facial and neck skin, reported differences in vocalizations (summarized in del Hoyo and Collar 2014), and because introgression appears to be limited (e.g., Zimmerman et al. 1996), although also poorly studied: a monotypic Eastern Crested Guineafowl Guttera pucherani; a polytypic Western Crested Guineafowl Guttera verreauxi, with subspecies sclateri and verreauxi; and a polytypic Southern Crested Guineafowl Guttera edouardi, with subspecies barbata and edouardi.

Within Western Crested Guineafowl, reposition nominate verreauxi to precede, rather than follow, subspecies sclateri.

References:

del Hoyo, J., and N.J. Collar. 2014. HBW and BirdLife International illustrated checklist of the birds of the world. Volume 1. Lynx Edicions, Barcelona.

Zimmerman, D.A., D.A. Turner, and D.J. Pearson. 1996. Birds of northern Kenya and northern Tanzania. Princeton University Press, Princeton, New Jersey.