Avifauna of the Van Rees Mountains, New Guinea

Abstract

Summary. We describe results of the first ornithological exploration of the uplands of the Van Rees Mts., the lowest of New Guinea's ten outlying mountain ranges. The narrow Mamberamo River gorge separates them from the higher and more species-rich Foja Mts. The known avifauna of Van Rees comprises 223 species, of which 17 are winter visitors from Australia or the Palearctic (occurring overwhelmingly in open non-forest habitats), and 37 are upland species. Whilst most of the Van Rees upland species occur in the Foja Mts., conversely most Foja upland species are unrecorded from Van Rees. Of course, upland species whose Foja elevational floors lie above the Van Rees summit are predictably absent from the latter. However, there are also many ‘flagrant absentees’ from Van Rees—i.e., conspicuous or abundant Foja species that could or ‘should’ occur in Van Rees because their Foja floors lie well below the Van Rees summit. The percentage of Foja upland species occurring in Van Rees increases with decreasing Foja floor elevation. That is, availability of elevationally suitable habitat does not provide an all-or-nothing explanation, but only increases the probability, of upland species success in colonising Van Rees. Our Van Rees records of non-forest species at natural clearings in forest—landslides, mud volcanoes, streams and lakes—illustrate how the region’s endemic non-forest bird species may have evolved, despite forest being the climax vegetation over most of New Guinea. The lake Danau Bira and its surrounding marsh, created by a mud volcano damming a stream, support at least 23 water and marsh species. An appendix summarises records and elevational ranges of all 223 species recorded in the Van Rees Mts.