Home range sizes of 11 bird species on a 10-ha forest site in southeast Australia

We used a simple and objective method of determining home range size for individuals of a bird community in southeast Australia. The community consisted of 11 species, which represented nine genera, five families, and a range of diets and nesting behaviors. The vegetation on the 10-ha site comprises a mixture of eucalypt forest; dense thickets of cycads, casuarinas, and ti-tree; a bushy and grassy powerline clearing 30-m wide running the length of the site; 1 ha of dense swamp paperbark trees; several small dams containing various reeds; and a riparian environment of a variety of different shrubs. Data were collected from 490 color-banded individuals of both sexes over seven to eight breeding seasons, and between 40 and 966 sightings were recorded per species. Species was a significant predictor of home range size (26% of the variance), but this was mainly because three species had large home ranges compared to the remaining species, which had similar but variable home ranges. Breeding season (as indicated by year), sex, and number of pairs were also significant predictor factors but together accounted for only 4% of the variance. The Southern Oscillation Index (a measure of the El Niño-Southern Oscillation, a major climate factor that is related to rainfall in eastern Australia) was not a significant predictor. The high residual variation (70%) indicated that each species had inherently variable home range sizes. Home range sizes were generally dissimilar (both lower and higher) to those of the same species in the literature but are consistent year to year at our study site. We suggest that wide variation in home range sizes of species is the result of both between-site habitat variation and within-site microhabitat variation, and is therefore not unexpected.