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Javan Hawk-eagle Nisaetus bartelsi
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The population of this impressive raptor is very small. Moreover, given the destruction, disturbance and degradation that is currently being inflicted on its preferred habitat, it is likely to be declining and increasingly fragmented, a circumstance that qualifies it as Endangered.

Taxonomic source(s)
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Taxonomic note
Spizaetus nanus, S. lanceolatus, S. philippensis, S. pinskeri, S. nipalensis, S. alboniger and S. bartelsi (Sibley and Monroe 1990, 1993) and S. cirrhatus and S. floris (Gjer

60 cm. Medium-sized, forest-dwelling eagle. Crown and moustachial of adult are black, long crest (often held almost vertically) is black, tipped white. Chestnut sides of head and nape, dark brown back and wings, brown long tail, barred black. Creamy-white throat with dark mesial stripe. Rest of underparts whitish, barred rufous. Immature is similar, but with plainer underparts and duller head. Similar spp. Changeable Hawk-eagle Spizaetus cirrhatus lacks rufous cheeks and long crest. Crested Honey-buzzard Pernis ptilorhynchus is smaller with a shorter crest, uneven tail-barring and less rufous in plumage. Rufous-bellied Eagle Hieraaetus kienerii has shorter crest and extensive white upper breast streaked black.

Distribution and population
Spizaetus bartelsi is endemic to the island of Java, Indonesia, where it is restricted to remaining patches of forest and is consequently scarce (BirdLife International 2001). An increase in survey effort and knowledge of the species's home-range size has led to consecutive upward revisions of the global population, now estimated at over 600 individuals (Prawiradilaga 2004), with one estimate of 270-600 pairs (Gjershaug et al. 2004). It is distributed widely throughout much of the island with a recent increase in the number of known localities, although it remains unrecorded from large areas of the north. Although there is no direct indication of a decline, with the species always considered rare, the on-going diminution of forest-cover on Java and increasing trade in the species are certain to have been detrimental (Nijman et al. 2009).

Population justification
The population is estimated to number 600-900 individuals, roughly equating to 300-500 mature individuals, based on a 1:1 ratio of adults to juvenile and immature birds, as recorded in past studies (B. van Balen in litt. 2012).

Trend justification
This species is suspected to be in decline at a moderate rate, owing to on-going habitat loss and degradation in the face of human population growth, combined with capture for trade. Recent nest protection may have improved reproductive success, but the benefits accrued may have been countered by an apparent increase in trade of this species following its elevation to national bird.

It frequents primary humid forest, although individuals and even nests have been recorded in secondary forest, production forest and tropical semi-deciduous forest, preferring rugged slopes with high vegetation cover (Syartinilia and Tsuyuki 2008). While it occurs from sea-level to high mountains, it is most frequent at 500-1,000 m. Recent extensive research has estimated the average home range size of one pair to be c.400 ha (Gjershaug et al. 2004). The species's dispersal capabilities (and therefore its susceptibility to habitat fragmentation) remain poorly known, but adults appear to be highly sedentary while young birds are the main dispersers (Nijman and van Balen 2003). Juveniles and immatures are recorded in woodland and some cultivated habitats before moving to secondary and primary evergreen forest as adults (Nijman and van Balen 2003); this behaviour suggests that unsuitable habitats may not represent barriers to dispersal. It breeds every two years, principally between January and July, but can breed at any time of year (Prawiradilaga 2006); its reproductive output is generally considered to be low (Syartinilia and Tsuyuki 2008). The preferred diet consists of small mammals but it will take birds, snakes and lizards (Prawiradilaga 2006).

The key threats are habitat loss and trade. The burgeoning human population on Java brings with it intense pressure on natural resources, one aspect of which has been a massive reduction in forest cover, particularly in the lowlands. This threat continues in the form of conversion to agriculture, development and uncontrolled fire, even within protected areas. The species is also sold openly in Javan bird markets, with 30-40 reported in trade each year, and presumably many more undetected. This threat appears to be intensifying, following the elevation of the species to national bird. Individuals are taken from the wild for zoos and wildlife collections, where they tend to fare poorly (Nijman et al. 2009).

Conservation Actions Underway
CITES Appendix II. Several surveys have targeted the species, exploring its distribution and ecology (Prawiradilaga 2006). Strict legislation protects it from hunting or trading, although this is often ineffective. It occurs in several protected areas, including Gunung Halimun, Gunung Gede-Pangrango and Meru Betiri National Parks, although these still face serious problems. An action plan has been compiled and conservation awareness programmes including several training and awareness raising workshops have been initiated (Prawiradilaga 2006, Narwatha et al. 2007). Project Garuda, which ran in 2002-2003 in Butahu, West Java, combined research with conservation activities implementing an extensive awareness raising programme including radio broadcasts, school visits and an exhibition (Narwatha et al. 2007). A nest protection programme involving local communities has been run successfully (Prawiradilaga 2006). Regular monitoring occurs in Telaga Warner Nature Reserve, Gede-Pangrango National Park and parts of G. Halimum-Salak National Park (Prawiradilaga 2006) and surveys took place around Butahu in 2002-2003 (Narwatha et al. 2007). A captive breeding programme has been underway since 1996, although as of 2006 it had failed to produce any offspring (Nijmal et al. 2009).
Conservation Actions Proposed
Implement the Javan Hawk-eagle Recovery Plan. Continue ecological studies to allow appropriate management regimes to be devised. Improve management of existing protected areas, and establish further reserves, particularly in central Java, at Dieng Mountains and Gunung Slamet, and West Java in southern Cianjur district. Manage these protected areas as an established and connected network of sites, with the help of local stakeholders. Focus future population surveys on areas predicted but not confirmed to hold populations of the species (Syartinilia and Tsuyuki 2008). Continue to search for and guard nests found near human populations. Improve and enforce legislation to control trade. Continue and expand education schemes to elicit public support for the conservation of this and other threatened species on Java.

BirdLife International. 2001. Threatened birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, U.K.

Gjershaug, J.O.; Rov, N.; Nygard, T.; Prawiradilaga, D.M.; Afianto, M. Y.; Hapsoro; Supriatna, A. 2004. Home-range size of the Javan Hawk-eagle (Spizaetus bartelsi) estimated from direct observations and radiotelemetry. Journal of Raptor Research 38(4): 343-349.

Nijman, V.; Shepherd, C. R.; van Balen, S. 2009. Declaration of the Javan Hawk Eagle Spizaetus bartelsi as Indonesia's National Rare Animal impedes conservation of the species. Oryx 43(1): 122-128.

Nijman, V.; van Balen, S. B. 2003. Wandering stars: age-related habitat use and dispersal of Javan Hawk-eagles (Spizaetus bartelsi). Journal für Ornithologie 144: 451-458.

Prawiradilaga, D. 2004. Javan hawk-eagle (Spizaetus bartelsi). Fauna and Flora 6: 29.

Prawiradilaga, D. M. 2006. Ecology and conservation of endangered Javan Hawk-eagle Spizaetus bartelsi. Ornithological Science 5(2): 177-186.

Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Sibley, C. G.; Monroe, B. L. 1993. A supplement to 'Distribution and taxonomy of birds of the world'. Yale University Press, New Haven, USA.

Syartinilia; Tsuyuki, S. 2008. GIS-based modelling of Javan Hawk-eagle distribution using logistic and autologistic regression models. Biological Conservation 141(3): 756-769.

van Balen, S. 2000. The Javan hawk-eagle: misconceptions about rareness and threat. Biological Conservation 96: 297-304.

Further web sources of information
Detailed species accounts from the Threatened birds of Asia: the BirdLife International Red Data Book (BirdLife International 2001).

Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Benstead, P., Bird, J., Khwaja, N., Taylor, J. & Tobias, J.

van Balen, B.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2016) Species factsheet: Nisaetus bartelsi. Downloaded from on 27/10/2016. Recommended citation for factsheets for more than one species: BirdLife International (2016) IUCN Red List for birds. Downloaded from on 27/10/2016.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Javan hawk-eagle (Spizaetus bartelsi) 0

Key facts
Current IUCN Red List category Endangered
Family Accipitridae (Hawks, Eagles)
Species name author (Stresemann, 1924)
Population size 300-500 mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 14,500 km2
Country endemic? Yes
Links to further information
- Additional Information on this species