The mountain serpent eagle (Spilornis kinabaluensis) is a fierce-looking, forest-dwelling eagle found only on the island of Borneo. A relatively small eagle, it has dark brown plumage that is paler and speckled on the underparts. The flight feathers of the long wings have black tips and white bases. The head and throat of the mountain serpent eagle are black with light speckles on the back of the neck (4), and it has a short, bushy crest of feathers on top of the head (5).
The long, dark tail of the mountain serpent eagle has a thick white band running across it, a feature that differentiates it from its close relative the crested serpent eagle (Spilornis cheela), which has a less distinctive greyish-white tail band. The mountain serpent eagle also has larger wings, smaller speckles and is generally darker in appearance than the crested serpent eagle (4).
Like all birds of prey, the mountain serpent eagle has an incredibly sharp, hooked beak, used for tearing apart its prey. The talons and beak are bright yellow and stand out against the dark body (6).
The call of the mountain serpent eagle is a repeated, high-pitched whistle (2).
- Also known as
- Kinabalu serpent-eagle, mountain serpent-eagle.
- Spilornis cheela kinabaluensis.
- Culebrera del Kinabalu.
- Length: 51 - 56 cm (2)
Mountain serpent eagle biology
For many years the mountain serpent eagle was assumed to be a subspecies of the crested serpent eagle (Spilornis cheela), Borneo’s most common eagle (7) (8). Due to this, and the fact that its habitat is often difficult to access, little is known about the biology of this rare bird (6).
The mountain serpent eagle is often seen soaring over ridge tops (6). It has been reported to feed on snakes and lizards, including anglehead lizards (Gonocephalus species) (9).
Information on the breeding biology of the mountain serpent eagle is also scarce. In one case, adults were seen with two juvenile birds in November (9).
Mountain serpent eagle range
The mountain serpent eagle is found only in Borneo. It is restricted to the mountains of central and northern Borneo, in Brunei, Malaysia and Indonesia (2).
Mountain serpent eagle habitat
Mountain serpent eagle status
The mountain serpent eagle is classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).
Mountain serpent eagle threats
The greatest threats facing the mountain serpent eagle are habitat loss and degradation. This is mainly due to logging and the expansion and intensification of agriculture, forcing rainforest to be converted into oil palm, rice, maize, sugar and coffee crops (6).
However, because the mountain serpent eagle is found at high altitudes and in remote locations, it is secure in many parts of its range (6).
International trade in the mountain serpent eagle should be strictly controlled under its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (3). This bird is protected in Sarawak, and it occurs in Kinabalu Park in Sabah and Gunung Mulu National Park in Sarawak, where its habitat is protected (2) (9).
Outside of these parks there are no specific conservation measures in place for the mountain serpent eagle, as it is found at altitudes which are beyond logging and agricultural activities and is therefore assumed to be relatively secure in these parts of its range (2) (6).
However, a number of conservation actions have been recommended for this species, including conducting research to accurately estimate its range and population, and to assess the degree of threat from habitat destruction. It is proposed that a large area of the mountain serpent eagle’s habitat in the Bornean highlands should be protected, and the areas that are currently protected should be properly managed (2) (6).
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Find out more about the mountain serpent eagle and its conservation:
Find out about conservation in Borneo:
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- Evergreen rainforest
- Rainforest consisting mainly of evergreen trees, which retain leaves all year round. This is in contrast to deciduous trees, which completely lose their leaves for part of the year.
- Flight feathers
- The feathers at the end of the wing, involved in flight.
- Of mountains, or growing in mountains.
- Submontane forest
- Forest occurring in the foothills or lower slopes of a mountainous region.
- A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
IUCN Red List (November, 2010)
BirdLife International - Mountain serpent eagle (November, 2010)
CITES (November, 2011)
MacKinnon, J. and Phillipps, K. (1993) A Field Guide to the Birds of Borneo Sumatra, Java and Bali. Oxford University Press, New York.
Ferguson-Lees, J. and Christie, D.A. (2001) Raptors of the World. Christopher Helm, UK.
Stattersfield, A.J. and Capper, D.R. (2000) Threatened Birds of the World. Lynx Edicions and Birdlife international, Cambridge.
Sibley, C.G. and Monroe Jr, B.L. (1990) Distribution and Taxonomy of Birds of the World. Yale University Press, London and New Haven.
Smythies, B.E. (1960) The Birds of Borneo. Oliver and Boyd Ltd, Edinburgh.
BirdLife International (2001) Threatened birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK.