Resit Sözer

Breeding Biology of Javan Hawk-eagle Spizaetus bartelsi in West Java, Indonesia

Summary The Javan Hawk-eagle Spizaetus bartelsi is one of the rarest and least known birds of prey, regarded as globally endangered and confined to the last remnants of forests left on the densely populated island of Java, Indonesia. Its biology is little-known and only a few cases of breeding have been reported. Systematic observations in 1992 and 1994 of two breeding pairs in the rainforest of the Gede-Pangrango National Park, West Java, are described in this paper. In total over 100 h of observation were made and covered different stages of the breeding cycle. Clutches consisted of one egg, incubated for 47 ± 1 days predominantly by the female, to whom the male brought prey. After the egg hatched the female joined the male in hunting. The male was rarely seen on the nest as copulation and prey transfer took place mainly on nearby trees. After fledging the eaglet stayed near the nest for at least two months. A prolonged post-fledging period followed, the juvenile remaining with its parents for more than one year.

Distribution and conservation of the Javan Hawk-eagle Spizaetus bartelsi

Summary The Javan Hawk-eagle Spizaetus bartelsi is endemic to the island of Java. Severe habitat fragmentation and small population size, aggravated by illegal hunting have put this rainforest species on the list of threatened bird species. Intensive searching since 1986 resulted in the discovery of a large number of localities additional to the historic ones. All known locality records of Javan Hawk-eagle have been scrutinized and are listed in the present paper. Confirmed post-1980 records are from 24 forest fragments of varying sizes: 10 (including 28 discrete localities) in west, seven (including 14 discrete localities) in central and seven (including 20 discrete localities) in east Java. The configuration of available habitat in forest clusters is evaluated. The co-existence with other threatened bird taxa, and the need for further field surveys and studies of the Javan Hawk-eagle are discussed.

Effects of ENSO-induced forest fires and habitat disturbance on the abundance and spatial distribution of an endangered riverine bird in Borneo

Droughts induced by the 1997–1998 El Nino Southern Oscillation (ENSO) event sparked large-scale forest fires affecting millions of hectares on Borneo. We studied the effects of ENSO-induced disturbances on a riverine bird, the critically endangered white-shouldered ibis, Pseudibis davisoni, along the Mahakam River in East Kalimantan, Indonesian Borneo. Island-wide fire hotspots were more likely to occur near rivers and part of our study area was indeed affected by fire. Based on 25 boat surveys (2590 km) that yielded 91 records, we recorded significant changes in abundance and spatial distribution of this bird in our study area. Encounter rates were higher during the pre-ENSO (1992–1996) periods than the post-ENSO (1997–2000) ones and differed between seasons. No ibises were seen post-ENSO along river sections that were affected by the fires, whereas pre-ENSO encounter rates were 2.4 birds/102 km. Encounter rates along those sections that were not affected by the forest fires more than doubled from 2.0 birds/102 km pre-ENSO to 5.6 birds/102 km post-ENSO. This was most probably due to enhancement of displaced birds. In view of the permanent character of the change in spatial distribution, active protection of the remaining stretches of riverine forest is of the utmost importance for the survival of white-shouldered ibis.

New information on the distribution of Chestnut-bellied Partridge Arborophila javanica in the central parts of Java

Summary The Chestnut-bellied Partridge Arborophila javanica is confined to the hill and mountain forests of Java. Until recently, its range was thought to be restricted to the western and eastern part of the island. Surveys performed in March-September 1994 in the central part of the island showed it to be present there as well. The species was found in six remnant forest patches where it was not known to occur. Data on habitat preferences and altitudinal distribution are given. Puyuh-gonggong Jawa Arborophila javanica hanya dapat dijumpai di hutan-hutan pegunungan di Pulau Jawa. Dahulu jenis ini diperkirakan hanya tersebar di bagian Barat dan Timur pulau ini saja. Sebuah survey yang dilakukan pada bulan Maret-September 1994 di bagian tengah pulau menunjukan keberadaan jenis ini. Jenis ini dijumpai di enam lokasi yang merupakan sisa-sisa hutan. Data mengenai habitat dan distribusi berdasarkan ketinggian dipertelakan dalam tulisan ini.