A large bird of lowland and montane forest on the Sulu Islands, although probably only remaining on Tawi-Tawi. Feeds particularly on fig trees. One of the rarest birds in the world. Entirely black except for a white tail. Has a long, thick black bill, a black casque, and black bare skin around the eye. Male has pale eyes and female has brown eyes and a smaller casque. Unmistakable. The only hornbill in its range. Voice is a nasal cackling.