INTRA-SPECIFIC ABUNDANCE-DISTRIBUTION RELATIONSHIPS

Mechanisms that have been proposed to explain the relationship between abundance (mean abundance at occupied sites) and distribution (propor tion of sites occupied) have been based on (1) differences among speci es that affect either their ability to exploit resources or their abil ity to move through the landscape, (2) differences in species' landsca pes that affect rates of successful dispersal of individuals, or (3) s tatistical arguments. Existence of an intra-specific abundance-distrib ution relationship where species differences cannot be a factor would provide evidence that differences in species' landscapes likely contri bute to the inter-specific abundance-distribution relationship. We exa mined the intra-specific relationship between abundance and distributi on for 20 species of boreal forest songbirds. Abundance and distributi on were calculated for each species in 52 to 119 locations over an are a of 300 km x 100 km of northwestern Ontario. Based on separate regres sions, 16 of the species demonstrated significant positive relationshi ps between abundance and distribution at alpha = 0.05. The weighted me an partial correlation for all species combined was greater than zero (P < 0.05). Meta-analysis indicated that there is no significant varia tion in the abundance-distribution correlation among species. This stu dy provides evidence that amount of habitat within a landscape contrib utes to a positive intra-specific abundance-distribution relationship and therefore suggests that this factor could also contribute to the p ositive abundance-distribution relationship that is commonly found amo ng species within an assemblage.