Behavioural ecology, distribution and conservation of the Javan Hawk-eagle Spizaetus bartelsi Stresemann, 1924

In the period December 1993 – January 1995 research on the behavioural ecology, distribution and conservation of the Javan Hawk-eagle Spizaetus bartelsi was carried out by R. Sözer and V. Nijman, under supervision of BirdLife International / PHPA – Indonesia Programme. This research was part of the requirements for graduation in the study of Biology at the University of Amsterdam (UVA). During the seven-month of fieldwork many new data were collected on these subjects and recommendations for the conservation of the Javan Hawk-eagle were formulated. The main research aims were: 1) a study of the home range, habitat requirements and behaviour of the Javan Hawk-eagle, and 2) a study of the distribution of the hawk-eagle with special reference to the central part of Java. This area was as yet unknown to hold populations of the species. Some background information on the biodiversity of Java, its geology and climate, natural vegetation and characteristic mountain birds, is presented. An overview of all Spizaetus species, their taxonomy and systematics is given. Furthermore, accurate descriptions of S. bartelsi for positive identification in the field as well as in museum collections are made. Sonagrams of the species’ call are presented. A total of 16 areas was surveyed; S. bartelsi was found in nine areas, six of these being new localities for the species. Taking these new localities into account, the population size was estimated, resulting in an increase from 52-61 to 81-108 pairs. Most Javan Hawk-eagles were observed in primary forest and the ruggedness of the terrain was a common feature of all localities. The visable homerange was 12km² but realistic estimates gave homerange sizes between 33km² [Gn Slamet] and 155km² [Alas Purwo N.P.], varying with suitability of the habitat. During 114 contact hours with a breeding pair, and a pair together with their second year young, many new data were gathered on the behaviour and ecology of the species, e.g. the breeding period was determined at 47 +/- 1 days, the breeding season was calculated and copulation observed. Courtship displays, nest tree and nest maintenance are described. Sexual dimorphism was quantified by measuring 23 museum specimens. Even though the new population estimate is more positive than earlier estimates, the fact remains that less than 10% of Java is covered with natural forest, not all of which is suitable habitat for the Javan Hawk-eagle. The combination of this lack of habitat and the its low reproductive rate (36 – 45 young per year for the entire population) make the species one of the world’s most endangered raptors. In addition, the species is not suitable for captive propagation, but nevertheless 10 specimens arrived in zoos in 1994 of which three died during the same year. Available habitat is the limiting factor for the wild population and destruction of its natural environment is the eagle’s main threat. Four areas are recommended as priority areas for conservation of S. bartelsi habitat; in order of significance: 1) The Dieng Mountains, 2) Gn Slamet, 3) Pegunungan Pembarisan and Gn Segara, 4) Gn Wilis-Liman. Further recommendations for the conservation of the Javan Hawk-eagle include: more effective law enforcement, confiscation of illegally kept specimens, prosecution of violators, restriction of numbers legally held in captivity, monitoring of birdmarkets, further conservation research. In conclusion, the Javan Hawk-eagle, the national symbol of Indonesia [Garuda], and symbol of all rare species, need not become extinct if its natural habitat is effectively preserved and other threats eliminated.