Summer rainfall and winter sparrow densities: a test of the food limitation hypothesis.

Abstract

Abundance of seeds available to wintering granivorous birds is correlated with the quantity of rainfall the previous summer. Results strongly support 2 a priori predictions: 1) the density of sparrows should be positively correlated with summer rainfall, and 2) the density of individual sparrow species should be positively correlated with the total density of all other sparrow species. Winter finch populations are food-limited. Interspecific competition may be important in at least some avian communities. -from Authors