Dry-Season Bird Diversity in Tropical Rainforest and Surrounding Habitats in North-east Australia

A quantitative analysis of bird species richness and abundance in habitats in and adjacent to rainforest in northeast Queensland, Australia, is presented. Bird assemblages in five habitats surrounding tropical rainforest were compared using line transects over a six-week period in the winter dry-season, between July and September 1995. Data were analysed using the Shannon–Weaver index of biodiversity and by a rarefaction method. Avian biodiversity was more variable between sites than between habitat types. While no habitat stood out at either extreme, diversity was highest in an area of riverine rainforest. Rainforest interior proved one of the poorest habitats for bird diversity. However , species assemblages were different among habitats, with 38% of species being found in only one habitat type. While it is clear that habitat destruction endangers biodiversity (Wilson 1992; Balmford & Long 1994), in the current economic and political climate the emphasis on ecological aims is to accept change as inevitable, but then fight for the lesser of the many evil options (Caldecott et al. 1997). Diversity studies remain as important subjects for research for three reasons: (1) global biodiversity proves hard to assess (Gaston & Blackburn 1995; Williams et al. 1997) and consequently it is still a fundamental priority (see Gaston 1996); (2) mechanisms underlying biodiversity are still not understood (eg. Stevens 1989; Blackburn & Gaston 1996); and (3) methods to mitigate habitat destruction and conserve maximum biodiversity are vague, as a consequence of a paucity of information about (1) and (2). Australian rainforests contain 2500 species of flowering plants, 70% of which are endemic to Australia (Collins 1990) and 23 species of endemic birds (Long et al. 1996), as well as some species which are considered 'endangered' or which have other threatened status (Baker-Gabb 1994; Collar et al. 1994). Little ornitholog-ical work has been conducted in the tropical rainforests of northeast Australia. Several authors have studied foraging ecology of birds in Queensland in both low-land (Crome 1975, 1978) and upland rainforest (Frith 1984) and also in lowland rainforest in New Guinea (Bell 1982a, b; Beehler 1981). But quantitative studies detailing bird diversities in different habitat types are few and baseline data with which to compare future studies have recently been called for (Mac Nally 1997). This study is also pertinent to contemporary conservation biology because transient rainforest edge habitats have been claimed to be very diverse, and because with increasing human impact on rainforest there is …