Attributes / relations provided by
♦ ¹del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.
♦ ²Seed dispersal by Ceratogymna hornbills in the Dja Reserve, Cameroon, KENNETH D. WHITNEY, MARK K. FOGIEL, AARON M. LAMPERTI, KIMBERLY M. HOLBROOK, DONALD J. STAUFFER, BRITTA DENISE HARDESTY, V. THOMAS PARKER and THOMAS B. SMITH, Journal of Tropical Ecology (1998) 14:351–371