INTERSPECIFIC DIFFERENCES IN INTRASPECIFIC ABUNDANCE-RANGE SIZE RELATIONSHIPS OF BRITISH BREEDING BIRDS

A general positive interspecific relationship between local abundance and geographic range size in animals has prompted speculation that a s imilar relationship might exist intraspecifically, such that a species is widespread at times when it is locally abundant, and more restrict ed in distribution when it is locally rare. Current evidence suggests thar intraspecific relationships often are positive, but that there is considerable variation in the pattern exhibited by species. Here, we use data on British birds to test the hypotheses that species showing a high mean or wide spread of local densities or range sizes will be m ore likely to show strong intraspecific relationships between abundanc e and geographic range size. These data show only inconsistent support for an effect of the range of densities or of occupancies on intraspe cific abundance-range size relationships. However, the strength of an intraspecific relationship does seem to be related to the mean occupan cy of species, and whether or not a species exhibits temporal trends i n density, with the strongest relationships found in species with simu ltaneous trends in both density and occupancy. We suggest that these r esults are explained by time lags in the loss or gain of species at oc cupied sites in response to reductions or increases in density.