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Bawean Serpent Eagle
Spilornis baweanus

Status: Critically endangered

Population Trend: Declining.

Other Names: Bawean Serpent-eagle.

Spilornis baweanus
click to enlarge
Distribution: Indomalayan. Endemic to INDONESIA (Bawean Island, north of JAVA and Madura).more....

Subspecies: Monotypic.

Taxonomy: This form has been regarded as a subspecies of the widespread Crested Serpent Eagle (S. cheela, by most authors (Stresemann and Amadon 1979, Amadon and Bull 1989, Sibley and Monroe 1990, del Hoyo et al. 1994), but Ferguson-Lees and Christie (2001) and Nijman (2004, 2006) treated it as a full species. They are followed here, pending a molecular genetics study of the entire genus Spilornis and because the different insular populations formerly assigned to S. cheela may have distinct, pressing conservation problems that might be overlooked if they are treated as subspecies.

Movements: Non-migratory.

Habitat and Habits: The only focused investigation of this species was conducted by Nijman (2006) during a 15-day period in September-October 2002. He found most eagles in or above tall forest and to a lesser degree in shrub and degraded forest. A few occurred in cultivated lands and teak plantations. Birds were not observed in or above a local palm forest, mangroves, or coastal forest, and they were only recorded from sea level to >500 m. They were frequently found near villages. Most eagles were observed as single birds and pairs, and more rarely seen in groups of three or four (Nijman 2004).

Food and Feeding Behavior: No information.

Breeding: Nijman (2004) observed these birds performing display flights during his visit to the island in late September-early October 2002. He also commented that the gonads of four birds collected in May-June were all small, suggesting that the species may breed in the wet season. Blouch and Admosurdirdjo (1979) also mentioned that breeding occurs from November to February. The nest and eggs have not been described.

Conservation: Critically Endangered. A 15-day survey in 2002 revealed that the species is present in very small numbers throughout the island of Bawean. Interviews with islanders revealed that recreational hunting, a relatively recent phenomenon, poses the greatest threat to the eagles and that the native forest on the island is poorly protected with widespread illegal logging and burning. Nijamn estimated the available habitat at only 92 kmē. Intervention by a conservation body, which might lead to protection of the birds and their habitat, is urgently needed (Nijman op cit.). Since this population is regarded as a race of the widespread Spilornis cheela by BirdLife International, its conservation status is not treated by that group.

Population Estimates: Based on his survey of Bawean in 2002, Nijman (2006) concluded that the total population may not exceed 60-75 adult birds.

Important References: 
Blouch, R.A., and S. Admosudirdjo. 1979. Usulan suaka margasatwa Pulau
  Bawean, pedoman pengolaan. World Wildlife Fund, Bogo, Indonesia.
Clark, W.S. 1994. Crested Serpent-eagle. P. 133 in del Hoyo, J., A.
  Elliott, and J. Sargatal (eds). Handbook of birds of the world. Vol. 2. New
  World vultures to guineafowl. Lynx Edicions, Barcelona, Spain.
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the world.
  Christopher Helm, London.
Hoogerwerf, A. 1962. Notes on Indonesian birds with special reference to
  the avifauna of Java and the surrounding small islands (I, II, III). Treubia
Hoogerwerf, A. 1966. Notes on the island of Bawean (Java Sea) with special
  reference to the birds (I). Natural History Bulletin of the Siam Society
Nijman, V. 2004. Surveys on birds of prey and owls (Falconiformes and
  Strigiformes) on Bawean, Java Sea, with records of three species new to the
  island. Raffles Bulletin of Zoology 52:647-651.
Nijman, V. 2006. The endemic Bawean Serpent-eagle Spilornis baweanus:
  habitat use, abundance and conservation. Bird Conservation International
Oberholser, H.C. 1917. The birds of Bawean Island, Java Sea. Proceedings
  of the U.S. National Museum 52:183-198.

Last modified: 9/3/2012

Recommended Citation: Global Raptor Information Network. 2020. Species account: Bawean Serpent Eagle Spilornis baweanus. Downloaded from http://www.globalraptors.org on 4 Jun. 2020

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