The anatomy of the interspecific abundance-range size relationship for the British avifauna: I. Spatial patterns

Data from the British Trust for Ornithology Common Birds Census and two atlases of breeding birds were used to examine the form of the interspecific abundance-range size relationship for the British avifauna. The relationship is positive for both farmland and woodland habitats and over two different periods, with some evidence of curvilinearity, using either proportion of occupied sites or numbers of occupied 10 x 10 km squares as measures of range size, and mean density at occupied sites as a measure of abundance. A log-linear plot gives the highest correlation. The relationship is stronger ii based on maximum local densities than if based on average densities, but there is no relationship using minimum local densities. Relationships based on abundances at individual sites are uniformly positive for all sites, although the relationships for many sites also show evidence of curvilinearity, especially when range size is measured as the proportion of occupied sites. Species show significant concordance in their rank abundances across sites. We discuss some implications of these results.