Journal of Ornithology

, Volume 145, Issue 3, pp 227–237 | Cite as

On ornamental maturation of two Philippine hornbill species with a note on physiological colour change

  • Eberhard Curio
Original Article


Two Philippine hornbill species, the Visayan writhed-billed hornbill (Aceros waldeni) and the Visayan tarictic hornbill (Penelopides panini panini), display on their heads multiple sexual ornaments in both sexes. An account is given of the maturation of these ornaments, except for the hood on the hind neck, from the nestling stage through age 5 years in the writhed-bill, and from fledgling stage through age 3+ years in the tarictic. Development proceeds in a staggered fashion, in that component traits of the compound ornament are added sequentially to a baseline already present in the nestling (bare facial skin) up until maturity. In same-aged pair mates of the writhed-bill, elements (dark grooves and wreaths in the red bill) were continually added until the reproductive age of 5 years, when observations ceased. Contrary to published accounts, only the writhed-bill passes through a male-like plumage in the nestling/fledgling stage, whilst the tarictic juveniles attain their sexually dimorphic appearance right away. Writhed-bill chicks exhibit a colour dimorphism of eye (= iris) colour irrespective of sex, in which the two phases pass through two stages, but in reverse order. At least part of the ornaments can be interpreted as honest indicators of condition. Based on the concept of honest signalling, the multiple nature of the ornamentation is functionally explained by the ‘multiple message hypothesis’. A physiological colour change between white and blue within seconds/minutes occurs in the bare facial skin patches of the tarictic and thus adds to the arsenal of hornbill multiple ornaments. This constitutes the first evidence for this type of colour change in a bird.


Hornbill Ontogeny Ornament Philippines Physiological colour change 



The work of the PESCP is formalised under the aegis of a Memorandum of Agreement with the Department of Environment and Natural Resources (Quezon City, Philippines). The help of the Protected Area and Wildlife Bureau (Directors W.S. Pollisco, R.C. Bayabos), and both RED J. Amador and RED V. Paragas (DENR Region VI, Iloilo) is gratefully acknowledged. The project is sponsored by the Frankfurt Zoological Society. Further support came from: Advocates of Bird Conservation; the German Aviculturists’ Association, President T. Pagel; CEPF through Haribon Foundation, Quezon City; the Daimler Benz AG; EED, Bonn; ‘GEO protects the rain forest’; GTZ/CIM of the German Government; German Ornithologists’ Society; IDEXX, Wörrstadt; Vitakraft-Werke; Sparkasse Bochum, Director Goldmann; Vogelschutz-Komitee (Bird Protection Committee), Prof. Dr. E. Schneider; and generous donations of Prof. Dr. Dr. mult. h.c. Ernst Mayr, Cambridge, Mass., USA; Prof. Dr. R. Dermietzel, Bochum; Mr Antonio de Dios, Quezon City; Mr. G. Gewers, Berlin. Further assistance came from project staff at Mag-aba, Dr. E. ‘Bembot’ Sanchez, in Bulanao, N. Bagac, at Sibaliw, especially ‘Jun’ B. Tacud, F. Geronimo and Dr. S. Luft. Great thanks to H. Schulze for her unstinting help with the illustrations, to L.L. Lastimoza, WVSU, for advice, and A. Hamann, Vancouver, T. Laman, USA, and J. Wolf, Landau, for photographs.


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V.  2004

Authors and Affiliations

  1. 1.Conservation Biology Unit, Faculty of BiologyRuhr-University BochumBochumGermany

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