Initial deadline for comments: 31 January 2012 [note that this has been moved back by about two months].
Yellow-casqued Hornbill Ceratogymna elata and Brown-cheeked Hornbill Bycanistes cylindricus inhabit forested areas in West Africa. C. elata occurs disjunctly from Senegal to Cameroon, while B. cylindricus has a more restricted distribution, occurring from Guinea to Togo. Both species prefer primary forest but may also occur in logged or secondary forest, as well as plantations (Thiollay 1985; Fry et al. 1988; Holbech 1992, 1996; Gartshore et al. 1995).
Both of these species are currently listed as Near Threatened under criteria A2c,d; A3c,d; A4c,d on the basis that they are undergoing moderately rapid declines (typically 20-29% over 10 years or three generations) owing to habitat loss, fragmentation and degradation and the impacts of hunting pressure.
BirdLife estimates the generation length for B. cylindricus at c.19 years, thus the trend should now be estimated over a three-generation period of 57 years. The generation length for C. elata is now estimated by BirdLife to be c.15.8 years, thus this species’s population trend should now be estimated over a period of 47 years.
Recent observations suggest that both species are in rapid decline in Ghana. Hunting pressure has led to the extirpation of both species from Bia National Park (NP), where there have been no records of either since 1991 (Dowsett-Lemaire and Dowsett 2011a), although both of them persist at a number of other sites, including small numbers of B. cylindricus at Atewa Range Forest Reserve (FR) and Tano Ofin FR, despite high hunting pressure at these locations (Dowsett-Lemaire and Dowsett 2009b). Surveys of Atewa Range FR over 16 days in June 2006 yielded records of B. cylindricus on only three occasions, including only one pair, perhaps owing to movements in search of food, but contrasting with more frequent observations in February 2005 (McCullough et al. 2007), possibly indicating depleted numbers.
Several hunters interviewed by Dowsett-Lemaire and Dowsett (2009b) in Ghana have said that B. cylindricus has become rare or difficult to find and, according to the forest guard at Fure Headwaters, the species might be extinct there. B. cylindricus may also have disappeared from Opro River FR (Dowsett-Lemaire and Dowsett 2010).
C. elata still occurs in eastern Ghana, albeit in very small numbers (Dowsett-Lemaire and Dowsett 2009b), which may not represent a viable population (Dowsett-Lemaire and Dowsett 2009a), but has been found to be common at Ankasa Resource Reserve (RR) (Dowsett-Lemaire and Dowsett 2010). C. elata has not been recorded at Atewa Range FR since 2005 at least, with perhaps the last confirmed record in May 2002 (per Dowsett-Lemaire and Dowsett 2011b).
Data and observations are requested from other parts of these species’ ranges to confirm whether the situation in Ghana is representative of their overall status. It is noted, however, that any assessment of population trends in these species must account for their movements in search of food resources. If evidence suggests that either species has undergone or is projected to experience a decline of at least 30% over three generations, they may be eligible for uplisting to Vulnerable. A rate of decline estimated to be at least 50% over three generations would qualify them for uplisting to Endangered.
Dowsett-Lemaire, F. and Dowsett, R. J. (2009a) Comments on forest reserves visited in eastern Ghana in 2009: wildlife (with special reference to birds) and conservation status. A report prepared for the Forestry Commission, Accra, Ghana. Dowsett-Lemaire Misc. Report 63.
Dowsett-Lemaire, F. and Dowsett, R. J. (2009b) Comments on selected forest reserves in SW Ghana: wildlife and conservation status. A report prepared for the Forestry Commission, Accra, Ghana. Dowsett-Lemaire Misc. Report 64.
Dowsett-Lemaire, F. and Dowsett, R. J. (2010) Comments on selected forest reserves visited in SW Ghana in 2009-2010: wildlife (especially birds) and conservation status. A report prepared for the Forestry Commission, Accra. Dowsett-Lemaire Misc. Report 67.
Dowsett-Lemaire, F. and Dowsett, R. J. (2011a) Ornithological surveys in Bia National Park and Resource Reserve, Ghana (January 2005, December 2009 and September 2010). A report prepared for the Wildlife Division, Forestry Commission, Accra. Dowsett-Lemaire Misc. Report 73.
Dowsett-Lemaire, F. and Dowsett, R. J. (2011b) An update on the birds of Atewa Range Forest Reserve, Ghana. A report prepared for the Wildlife Division, Forestry Commission, Accra. Dowsett-Lemaire Misc. Report 74.
Fry, C. H., Keith, S. and Urban, E. K. (1988) The birds of Africa vol III. London: Academic Press.
Gartshore, M. E., Taylor, P. D. and Francis, I. S. (1995) Forest birds in Côte d’Ivoire. Cambridge, U.K.: BirdLife International (Study Report 58).
Holbech, L. H. (1992) Effects of selective logging on a rain-forest bird community in western Ghana. University of Ghana, and University of Copenhagen (Thesis. MSc).
Holbech, L. H. (1996) Faunistic diversity and game production contra human activities in the Ghana high forest zone, with reference to the Western Region. Copenhagen:Zoological Institute/Museum, University of Copenhagen.
McCullough, J., Alonso, L. E., Naskrecki, P., Wright, H. E. and Osei-Owusu, Y. (Eds) (2007) A Rapid Biological Assessment of the Atewa Range Forest Reserve, Eastern Ghana. RAP Bulletin of Biological Assessment 47. Arlington, VA: Conservation International.
Thiollay, J.-M. (1985) The birds of Ivory Coast: status and distribution. Malimbus 7: 1-59.