Birds of the Illawarra District, 1982-87

Abstract

From 1982 to 1987, nine teams of observers performed bi-annual timed counts in autumn and spring (n = 12) to determine species richness, relative abundance, frequency of occurrence, distribution and diversity. Cumulatively, 61 observers counted 217 759 individuals of 238 species. In autumn and spring respectively, 198 and 217 species were recorded of which 104 (53%) and 122 (56%) were present in every count (n = 6). Thirty-one species were recorded only once in autumn (16% of total) and, by coincidence, also only once in spring (14% of total). The overall population comprised mostly residents (66%), passerines (42%) and species which preferred woodlands (31%) or wet-lands (30%). Species censused with highly variable numbers were the Silver Gull Larus novaehollandiae (53% to 21% of count totals) and Short-tailed Shearwater Puffinus tenuirostris (40% to zero). When these two species were excluded, there were significant seasonal differences in the number of other species present (average 12% higher in spring), the number of individuals counted (average 47% higher in autumn) and the indices of diversity of other species (average 24% higher in spring). Relative abundance, frequency of occurrence and distribution of all species are quantified in an appendix.