Abundance-range size relationships of breeding and wintering birds in Britain: a comparative analysis

Both breeding and wintering assemblages of birds in Britain exhibit positive interspecific relationships between population size and geographic range size, such that the average density of species is greater if they are more widely distributed. Species in common to both assemblages, that is resident species, had greater population sizes, geographic range sizes, and densities in winter. In contrast, whilst winter migrants had higher abundances than summer migrants, the range sizes of the former were disproportionately larger still, resulting in a lower density for species that only winter in Britain than for those that only breed. Such differences aside, the overall form of the abundance-range size relationship is remarkably similar between the two assemblages and their constituent subsets of species.