Kinabalu Serpent-eagle Spilornis kinabaluensis


Justification of Red List Category
Given the small range and relative mobility of this species, it is suspected to have a small population size (in a single subpopulation) that is suspected to be declining moderately rapidly as a result of ongoing habitat loss and degradation creeping up hill-slopes into its altitudinal range. It is consequently listed as Near Threatened.

Population justification
The area mapped (which accounts for suitable habitat and altitude) for this species encompasses c.156,000 km2. No density estimates of this species have been recorded, but Ferguson-Lees and Christie (2001) suggested a density of one pair/100 km2 (accounting for density and occupancy) recorded for S. cheela was appropriate to generate a global population estimate for the latter, equivalent here to c.3,120 mature individuals if applied to S. kinabaluensis. However, Ferguson-Lees and Christie (2001) also acknowledged that home ranges of S. cheela as small as 5-6 km2 had been recorded in optimum habitat. Applying this density to the range of S. kinabaluensis with a 30% occupancy gives a much greater value of 18,720 mature individuals. For these reasons, the population is suspected to comprise 2,500-19,999 mature individuals, with a most likely figure of 5,000-9,999 mature individuals. However, there is substantial uncertainty in this figure and acquiring species-specific density estimates should be considered a research priority. More qualitatively, the species is described as scarce in Sabah, but fairly common in Sarawak and Kalimantan (Eaton et al. 2021).

Trend justification
A population decline is suspected because of ongoing forest loss in its range. This species is highly forest dependent and is suspected to be declining at the same rate as forest loss; rates of forest cover loss have averaged c.9-11% over the last three generations [24 years; Bird et al. 2020] (Global Forest Watch [2021], using Hansen et al. [2013] data and methods disclosed therein) and this rate is suspected to continue into the future, although may in time begin to slow as higher altitude forest is less accessible.

Distribution and population

Spilornis kinabaluensis is confined to the mountains of central and northern Borneo in Brunei Darussalam, Sabah and Sarawak, Malaysia, and Kalimantan, Indonesia (BirdLife International 2001). From observations in the 1980s and 1990s, it appears to be a genuinely scarce species, with a small total population. However, much of its range is infrequently visited and it may prove to be more widespread than current indications suggest. It is likely to occur more or less continuously along the Crocker Range from Mount Kinabalu to Ulu Padas, G. Mulu and the border mountains of Brunei, and Gunung Murud (Pulong Tau National Park) (G. Davison in litt. 2007). Five individuals were seen in the Menyapa Mountains during surveys in 2007, which represents a southerly range extension for the species (Brickle et al. 2010), though the southern and western limits of its distribution are poorly known and need to be investigated, e.g., its occurrence in the Kelabit Highlands and Usun Apau, Kayan Mentarang and central montane parts of Kalimantan (G. Davison in litt. 2007, Mann 2008).


It is apparently sedentary in sub-montane and montane evergreen rainforest where it tends to prefer ridge-top forest at 750-2,900 m, although usually at 1,100-2,900 m (Eaton et al. 2021). In areas where it occurs alongside S. cheela it is separated altitudinally by a few hundred metres.


Habitat loss, degradation and fragmentation are the primary threats to the species, particularly towards the lower altitudinal limits of its distribution, where the extent of forest is diminishing in the face of agricultural expansion and intensification, although forest at higher altitudes is also threatened, for example by small-holder agriculture. Currently, rates of loss are relatively low (c.9-11% over three generations (Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein)), however this should be closely monitored. The species may occasionally be hunted, but this remains undocumented.

Conservation actions

Conservation and Research Actions Underway
CITES Appendix II. Occurs in multiple protected areas, including Kinabalu and Mulu National Parks and Temburong/Kuala Belalong (Brunei Darussalam).

Conservation and Research Actions Proposed
Conduct surveys to estimate density to inform a reliable population size of this species along with the degree of threat it faces from habitat destruction. Continue to use remote sensing data to monitor rates of forest loss in its range. Propose further sites for establishment as protected areas in the Bornean highlands. Ensure effective management of key protected areas for the species, including lending support to the 'Heart of Borneo' initiative. 


51-56 cm. Small, dark, forest-dwelling eagle. Plumage dark brown, speckled paler on underparts, wings and hindneck. Rich umber-brown patch on nape. Black throat. Fairly long, blackish tail with broad white band. Long wings with black tips and white bases to flight feathers. Similar spp. Its widespread relative, Crested Serpent-eagle S. cheela, is paler with shorter wings and narrower, less distinct greyish-white band on tail. Hints Frequently soars over ridge-tops and occurs at higher altitudes than S. cheela. Voice High repeated whistling notes similar to S. cheela.


Text account compilers
Berryman, A.

Benstead, P., Bird, J., Davidson, P., Davison, G., Eaton, J., Mann, C., Martin, R., Taylor, J., Tobias, J., Westrip, J.R.S. & van Balen, B.S.

Recommended citation
BirdLife International (2023) Species factsheet: Spilornis kinabaluensis. Downloaded from http://www.birdlife.org on 28/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/03/2023.