POPULATION-DENSITY, BODY-MASS AND NICHE OVERLAP IN AUSTRALIAN BIRDS

1. There is a negative relationship between body mass and ecological p opulation density across 200 species of Australian birds, with a slope of -0.82 on logarithmic axes. This is not significantly different fro m the slope predicted by the energetic equivalence rule. 2. Contrary t o previous studies, there is no tendency for the phylogenetic position of and individual tribe to correlate with the strength of the mass-de nsity relationship across its species. 3. However, in line with recent theory, there is a relationship between the degree of niche overlap a mong species in a tribe and the abundance pattern of the species. Trib es in which the species appear to share few resources are those in whi ch the relationship between mass and density is most strongly negative .