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Javan Hawk-eagle
Nisaetus bartelsi

Status: Endangered

Population Trend: Declining.

Other Names: Java Hawk-eagle, Java Hawk Eagle, Javan Hawk Eagle, Spizaetus bartelsi.

Nisaetus bartelsi
click to enlarge
Distribution: Indomalayan. Endemic to JAVA.

Subspecies: Monotypic.

Taxonomy: Traditionally placed in the genus Spizaetus, but recent molecular studies by Helbig et al. (2005) showed that the Asian hawk-eagle species represent a different lineage from the New World hawk-eagle species and should therefore be assigned to a new genus for which the name Nisaetus Hodgson 1836 is available. The same conclusion was reached independently by Lerner and Mindell (2005), based on the molecular sequences of one nuclear and two mitochondrial genes. Haring et al. (2007) also confirmed that Asian Spizaetus (Nisaetus) species are monophyletic and are distributed in two sub-clades, one of which consists of N. alboniger, N. bartelsi, N. nanus, and N. nipalensis. This species was formerly considered to be conspecific with N. nipalensis (Sibley and Monroe 1990), but is possibly closer to N. nanus (Brown and Amadon 1968).

Movements: Non-migratory, but juveniles disperse from breeding areas (Bildstein 2006).

Habitat and Habits: Occurs mostly in primary wet forest, although individuals and nests have been recorded in secondary forest, tree plantations, and tropical semi-deciduous forest (Prawiradilaga 2006). Birds spend most of their time perched, sometimes high in leafless trees or within the canopy. They soar during good weather.

Food and Feeding Behavior: Small mammals, including tree shrews, squirrels, bats, rats, and other small rodents are the preferred prey, but birds, snakes, and lizards are also taken (Prawiradilaga (2006). Prey is usually captured from a perch, but less commonly by soaring over the forest canopy and dropping on prey in a tree or on the ground.

Breeding: Breeding generally takes place between January and July, although there are nesting records from all months. The nest is a large structure made of sticks and leaves, lined with green leaves, and placed in a large tree. Nest sites are usually in undisturbed forest, but at least one was in a tree plantation (Afianto 1999). The species becomes sexually mature at the age of three or four years, and pairs breed every two years, if they are successful. Some juveniles may stay in the vicinity of their nest until the following year. The clutch size is 1 egg. The incubation period is 47-48 days (Sözer and Nijman 1995), and the nestling period is 70 days long (Prawiradilaga (2006). Both parents participate in feeding the young.

Conservation: Numbers of the Javan Hawk-eagle continue to decline because of threats to its remaining forest habitat, mostly from conversion to agriculture, development, and uncontrolled fire, illegal poaching, and capture for the pet trade, despite legislation banning such behavior. It was declared Indonesia's "National Rare/Precious Animal" in 1993, but Nijman et al. (2009) argued that this has actually led to an increase in interest in the species by the pet trade and more exploitation in the absence of effective regulation. There has been much research attention focused on this species, partly because it is the national bird. An action plan has been compiled, and a number of workshops on the species have been initiated (Prawiradilaga (2006). The Javan Hawk-eagle is categorized as Endangered by BirdLife International.

Population Estimates: Ferguson-Lees and Christie (2001) estimated the total global population, based on the number of adults and immatures at the start of the breeding season, in the range of 101 to 1,000 individuals. BirdLife International (2009) estimated the number of mature birds at 600 to 900 individuals, and owing to the large amount of research on the species, these figures are probably more reliable than those for any other Spilornis species.

Important References: 
BirdLife International. 2000. Threatened birds of the world. Lynx
  Edicions, Barcelona, Spain, and BirdLife International, Cambridge, UK.
Clark, W.S. 1994. Javan Hawk-eagle. Pp. 203-204 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. Houghton
  Mifflin, Boston, MA.
Hadi, F. 2000. Observations on the breeding behaviour of Javan Hawk-eagle
  (Spizaetus bartelsi). Pp. 145-154 in D. Prawiradilaga (ed.), Proceedings
  of the Second Symposium on Raptors of Asia. The Indonesian Committee for the
  Second Symposium of Asian Raptor Research & Conservation Network, Bogor,
Nijman, V., S. Van Balen, and R. Sözer. 2000. Breeding biology of Javan
  Hawk-Eagle Spizaetus bartelsi in West Java, Indonesia. Emu
Prawiradilaga, D.M. 2006. Ecology and conservation of endangered Javan
  Hawk-eagle Spizaetus bartelsi. Ornithological Science
Sözer, R., and V. Nijman. 1995. Behavioural ecology, distribution and
  conservation of the Javan Hawk-eagle Spizaetus bartelsi Stresemann, 1924.
  Verslagen en Technische Gegevens no. 62. Instituut voor Systematiek en
  Populatiebiologie (Zoologisch Museum), Universiteit van Amsterdam.
  Amsterdam, The Netherlands.
Sözer, R., V. Nijman, I. Setiawan, S. van Balen, D.M. Prawiradilaga, and
  J. Subijanto.
1998. Javan Hawk-eagle Recovery Plan 2. PHPA/BirdLife
van Balen, B.S., V. Nijman, and H.H.T. Prins. 2000. Javan Hawk-eagle:
  misconceptions about rareness and threat. Biological Conservation
van Balen, B.S., V. Nijman, and R. Sözer. 2001. Conservation of the
  endemic Javan Hawk-eagle Spizaetus bartelsi Stresemann, 1924 (Aves:
  Falconiformes): density, age structure and population numbers. Contributions
  to Zoology 70:161-173.
van Balen, S., R. Sözer, and V. Nijman. 1999. Distribution and
  conservation of the endemic Javan Hawk-eagle Spizaetus bartelsi. Bird
  Conservation International 9:333-349.

Sites of Interest:
Red Data Book Threatened Birds of Asia
Detailed information on status, threats, and conservation measures.

Gamauf, Anita
Gjershaug, Jan Ove
Mono, Hendry
Purwanto, Asman Adi
Setyawan, Bernadus
Suparman, Usep
Supriatna, Adam A.
Wijaya, Sasmita
Withaningsih, Susanti

Last modified: 6/11/2010

Recommended Citation: Global Raptor Information Network. 2020. Species account: Javan Hawk-eagle Nisaetus bartelsi. Downloaded from http://www.globalraptors.org on 25 Sep. 2020

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