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Grey-headed fish eagle in flight |
The genus of Asian fishing eagles Ichthyophaga, contain only two species: the grey-headed fishing eagle (I. ichthyaetus) and the lesser fishing eagle (I. humilis) (Brown and Amadon, 1968; Collar et al. 1994; del Hoyo et al. 1994). Whilst both species are broadly sympatric, ranging from northeast India, down the Thai-Malay Peninsula to Indonesia, virtually nothing is known of their specific ecological requirements in any part of their range (Ferguson-Lees and Christie, 2001).
Generalised reports suggest they are distributed in forests along rivers and lakes, on reservoirs and coastal swamp habitat on the Thai-Malay Peninsula (Wells, 1999), and in Sri Lanka, the grey-headed fishing eagle is thought to hunt in water storage tanks and is thus known locally as the ‘Tank Eagle’ (Henry, 1998). As their names suggest, both are considered to be specialist piscivores, thought to favour foraging from perches overhanging rivers and lakes (Baker, 1928; Brown and Amadon, 1968; Wells, 1999) and share a physiological foot adaptation (spicules) with the Osprey (Pandion haliaetus), another fish specialist.
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Nesting habitat at Prek Toal, Cambodia |
Whilst these two fishing eagle species are currently classified as globally near-threatened (Birdlife International, 2001), both are exhibiting range contraction and apparent population decline, for unknown reasons (Ferguson-Lees and Christie, 2001; Birdlife International, 2004), although potential threats are thought to include deforestation, pesticides and human disturbance (Baral and Inskipp, 2004).
We are collecting quantitative data on the ecology and habitat requirements of both species in the eastern part of their range (Cambodia) where both species exist in close proximity, to understand ecological niches and inform conservation planning.
The project is being run in collaboration with the Wildlife Conservation Society and has received funding from Natural Research (UK), The National Birds of Prey Trust (UK), Hawk Mountain Sanctuary (US) and The International Osprey Foundation (US).
In November/December 2005, our pilot study revealed a high-density population of grey-headed fishing eagles around the Tonle Sap Lake, probably the largest population in Indo-China. Our ecological studies revealed new information about the species’ foraging habits, including the discovery that the eagles’ diet includes the endemic water snake, a species heavily persecuted by locals for trade and food. A local Cambodian WCS biologist, Sun Visal, has been trained in raptor monitoring techniques and has been awarded (after being nominated by us!) a conservation internship at the internationally-acclaimed Hawk Mountain Sanctuary, USA.
Tingay, R.E., Nicoll, M.A.C. and Sun, V. Status and distribution of the grey-headed fishing eagle (Ichthyophaga ichthyaetus) in the Prek Toal Core Area of Tonle Sap Lake, Cambodia. Journal of Raptor Research 40(4): 277-283.
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WCS biologist, Sun Visal holding prey of fish eagles. |
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Nest of fish eagle |
Principal Investigators: Dr Ruth Tingay (Natural Research, ruth.tingay@natural-research.org) and Dr Malcolm Nicoll (University of Reading). All photos copyright R. Tingay.
REFERENCES CITED
Baker, E.C.S. (1928). The Fauna of British India including Ceylon and Burma, Volume V. Taylor Francis, London.
Baral, S.H. and Inskipp, C. (2004). The State of Nepal’s Birds 2004. Bird Conservation Nepal and IUCN, Kathmandu, Nepal.
Birdlife International (2001). Threatened Birds of Asia: The Birdlife International Red Data Book. Birdlife International, Cambridge, UK.
Birdlife International (2004). Red Data Book, Threatened Birds of Asia (updated): http://www.rdb.or.id
Brown, L.H. and Amadon, D. (1968). Eagles, Hawks and Falcons of the World. McGraw-Hill Book Company, New York.
Collar, N.J., Crosby, M.J. and Stattersfield, A.J. (1994). Birds to Watch 2: The World List of Threatened Birds. Birdlife International, Cambridge, UK.
del Hoyo, J., Elliott, A. and Sargatal, J. (1994). Handbook of the Birds of the World: New World Vultures to Guineafowl, Volume 2. Lynx Edicions, Barcelona, Spain.
Ferguson-Lees, J. and Christie, D.A. (2001). Raptors of the World. Houghton Mifflin, New York.
Henry, G.M. (1998). Guide to the Birds of Sri Lanka, 3rd Edition. Oxford University Press, India.
Wells, D.R. (1999). The Birds of the Thai-Malay Peninsula, Volume 1: Non-passerines. Academic Press, London.
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