The migration of raptors in the East Asian Flyway (in both Continental and Oceanic corridors) is still poorly understood (Ferguson-Lees and Christie 2001), and the complex geography of the region makes studying it challenging. Only recently a handful of pilot studies (Ash 1993; DeCandido et al. 2004; Germi 2005; Germi and Waluyo 2006; Nijman et al. 2006 ) concentrated along the continental corridor of the flyway, highlighted how much remains to be learned, and it is therefore no understatement to say that our understanding of raptor migration in this region is still very much in its infancy.
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Observation site on Sangihe |
At the southern end of the flyway within the vast Indonesian Archipelago, a system of island corridors leads to the heart of the zoogeographic subregion of Wallacea, which is believed to be the main wintering ground for several species of raptors from the eastern Palearctic. However, virtually no studies on raptor migration have been carried out in Wallacea, and only a handful of records are known (Meyer and Wiglesworth 1898; Coates and Bishop 1997; Riley 1997). Hence, in order to gather information on the magnitude of the passage, spatial and temporal distribution, and routes followed by migrants in this part of the flyway, Natural Research (UK) and Hawk Mountain Sanctuary (USA) are supporting a pilot study on the remote Indonesian island of Sangihe. Sangihe is strategically located along a chain of “stepping-stone” islands between Mindanao (Philippines) and Sulawesi (Indonesia), and it is likely a major concentration and passage point to the wintering areas of Wallacea. Two full-season counts will be carried out in Sangihe during spring and autumn 2007, in order to determine species and numbers using this oceanic corridor.
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Flock of migrating Chinese Sparrowhawks
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Our team made two full season counts, totalling over four months of field effort (Click here to go to our news page!). In autumn only we recorded more than 230,000 migratory raptors of the following species: Osprey Pandion haliaetus, Grey-faced Buzzard Butastur indicus, Chinese Sparrowhawk Accipiter soloensis, Japanese Sparrowhawk A. gularis, Harriers Circus sp., and Peregrine Falcon Falco peregrinus calidus. Chinese Sparrowhawk comprised approximately 98% of the flight, and our results and those from counts in other countries suggest that only a small percentage of this species global population overwinter west and north of Wallacea.
We estimate that at least 400,000 raptors are streaming into Wallacea each autumn from the Continental and Oceanic Flyways combined. The raptor migration into the relatively small land area of eastern Indonesia has been unappreciated, and our count results raise a number of questions about the wintering ecology of the species concerned. Furthermore, the scarcity of winter records throughout Wallacea suggests either that observer coverage in the region is still very poor, or that a large proportion of the migrants are dispersing into remote and poorly surveyed areas possibly as far as New Guinea, or both.
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Juvenile Chinese Sparrowhawk (Accipiter soloensis) |
A regional meteorological analysis is underway to establish relationships between weather and migration timing and magnitude along this section of the Oceanic Flyway.
We are drafting manuscripts for submission to peer-reviewed journals, and it will be in these journals that we hope to publish the full details of this important raptor migration.
A local Indonesian naturalist, Wesley Pangimangen, has been trained in raptor migration count methods, and he is now fully involved with the project. Wesley has previous work experience on the island’s endemics, in collaboration with BirdLife Indonesia Programme and the World Bank. As a result of his efforts on this study, Wesley has been awarded an International Internship in Conservation at Hawk Mountain Sanctuary (USA). Additional fieldwork is urgently needed to determine the wintering range of this large number of raptors, and to develop strategies for their future conservation.
Principal investigators: Francesco Germi (Francesco@germi.freeserve.co.uk) and Wesley Pangimangen.
Photos copyright F. Germi
References cited
Ash, J. S. (1993). Raptor migration on Bali, Indonesia. Forktail 9: 3-11.
Coates, B. J. and Bishop, K. D. (1997). A guide to the birds of Wallacea. Dove Publications, Alderley, Australia.
DeCandido, R., Nualsri, C., Allen, D. and Bildstein, K. L. (2004). Autumn 2003 raptor migration at Chumphon, Thailand: a globally significant raptor migration watch site. Forktail 20: 49-54.
Ferguson-Lees, J. and Christie, D. A. (2001). Raptors of the world. Christopher Helm, London.
Germi, F. (2005). Raptor migration in east Bali, Indonesia: observations from a bottleneck watch site. Forktail 21: 93-98.
Germi, F. and Waluyo, D. (2006). Additional information on the autumn migration of raptors in east Bali, Indonesia. Forktail 22: 71-76.
Meyer, A. B. and Wiglesworth, L. M. (1898). The birds of Celebes and neighbouring islands. Friedlander, Berlin.
Nijman, V., Germi, F. and van Balen, B. (2006). Relative status of two species of migrant sparrowhawks on Java and Bali, Indonesia. Emu 106 (2): 157-162.
Riley, J. (1997). The birds of Sangihe and Talaud, North Sulawesi. Kukila 9: 3-36.
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