Relationships between Distribution, Abundance and Foraging Specialization in Australian Landbirds

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Abstract
The distribution of landbirds throughout Australia is positively correlated with their distribution in the New England region of New South Wales, but only weakly, and negatively, correlated with local density. Local distribution is more strongly correlated with local density. This indicates that abundant species may tolerate or disperse into a range of habitats locally but that other factors influence their distribution on a continental scale, such as replacement by ecologically or phylogenetically similar species. Local density is positively correlated with niche breadth of foraging method and tree species, but not with niche breadth of substrate type or height. There are no positive correlations between any measures of distribution and niche breadth of foraging, though niche breadth for plant species is negatively correlated with breeding range. Thus, there is a tendency for generalists to be more abundant locally, but they do not appear to be more widespread. A broad foraging niche therefore does not seem to be the reason why widespread species may be locally abundant.