Currently known from just two, quite disjunct populations, one in central Peru and the other in central Bolivia, the Horned Curassow is considered Endangered globally by BirdLife International. The plumage is virtually all black, other than the white vent and tip to the tail; the bill is bright red and a pale blue casque erupts from the forehead. However, in the Bolivian subspecies, the casque is an upright horn, whilst in the Peruvian bird, the casque is flattened against the head, and is shorter and rounder. Furthermore, the Peruvian population also has a narrower white tip to the tail, and there are also differences in their vocalizations and habitat preferences. These differences have led to a recent proposal to treat the two populations as separate species. If this proposal is adopted, the tiny and highly range-restricted Peruvian population might warrant listing as Critically Endangered.