An overview of changes to the distribution and numbers of New South Wales birds was considered in relation to the IBRA bioregions, using data from Birds Australia's first and second national bird atlases (Atlas 1, 1977 - 1981 and Atlas 2, 1998 - 2001). Reporting rates, adjusted for survey effort, were compared for 347 bird species. Of these, 184 species (53%) showed no change between the two atlases, 83 (24%) were recorded more frequently during Atlas 2, and 80 (23%) were recorded less frequently during Atlas 2. This represents a greater proportion of declining bird species in NSW compared with the whole of Australia - one previous study found that 15% of 422 species had declined nationally. Of 139 woodland species tested, 33 (24%) were recorded less frequently during Atlas 2, a similar proportion to the broader pattern for all NSW bird species (23%). Woodland birds represented 41% of the declining bird species in NSW, 43% of the increasing species and 38% of species showing no change between the two atlases. Based on IUCN criteria, the current study indicates that 56 bird species may qualify as threatened in NSW. A brief case study is presented for one such species, the Gang-gang Cockatoo, which has subsequently been listed as threatened.
Our study also identifies possible drivers of regional patterns by modelling changes in reporting rate for individual woodland bird species against a selection of bioregional features from the National Land and Water Resources Audit, Landscape Health in Australia database. Bioregions with greater rainfall had increased reporting rates and greater woodland bird diversity in Atlas 2 compared with Atlas 1. Reporting rates for individual woodland bird species responded both positively and negatively to the % native vegetation cover and the % area grazed by livestock within bioregions.