 In the helmeted hornbill the casque is not hollow but is filled with hornbill ivory and is used as a battering ram in dramatic aerial jousts.Aerial casque-butting has also been reported in the great hornbill.The plumage of hornbills is typically black, grey, white, or brown, and is frequently offset by bright colours on the bill, or by patches of bare coloured skin on the face or wattles.Some species exhibit sexual dichromatism, where the coloration of soft parts varies by gender.