Birds on fragmented islands : persistence in the forests of Java and Bali

This study describes, analyses and provides suggestions for the amelioration of the impact of age-long deforestation on the distribution of forest birds on the islands of Java and Bali (Indonesia). The first section deals with colonisation and extinction processes of forest birds in a number of remaining forest patches on Java. In the regenerating forest of the Krakatau Islands colonisation and extinction of land birds appear to follow vegetation succession, and therefore seem to affect the monotonic change as predicted by MacArthur & Wilson's equilibrium theory of island biogeography.Extinction of forest birds in the Bogor botanical gardens appears to mirror closely the condition of bird communities in the surroundings of this isolated woodland patch. Distribution patterns of forest birds across 19 highly scattered forest fragments ranging from six to 50,000 hectares show clearly that the ability of birds to survive in surrounding habitat reflects the ability to survive in these patches. To show this, four ecological groups of forest birds have been distinguished: (1) forest interior birds, (2) forest edge birds, (3) woodland birds and (4) rural/urban birds. Nestedness patterns (in which species are found in all fragments larger than the smallest one in which it occurs) are found to be strongest for species restricted to forest interior and edge, weaker for secondary growth, and weakest for rural and urban bird species. A large number of forest interior species appear to be absent from most patches smaller than 10,000 ha, and most are entirely absent from forest patches smaller than 100 ha.In the second section of this thesis the conservation status of three globally threatened, high-profile birds is analysed. The endemic, endangered Javan hawk-eagle Spizaetus bartelsi , traditionally considered amongst the most vulnerable forest dwellers, appears to survive in 137-188 breeding pairs in often small and isolated rainforest patches; its survival is explained by (a) juvenile dispersal capabilities, (b) broader niche widths and (c) rather opportunistic feeding. Partly protected by local taboos on hunting, the vulnerable green peafowl Pavo muticus has survived many centuries of human pressure; nowadays at least 1000 birds are scattered across numerous subpopulations. The wild population of the endemic, critically threatened endemic Bali starling Leucopsar rothschildi collapsed since its discovery in 1910 to near extinction in 1990, due to habitat loss and popularity amongst bird-keepers world-wide; despite various conservation measures (captive breeding, awareness programmes, etc.) an intricate web of socio-economic factors prevents the species from emerging from this precarious situation.