The Effect of Agriculture on Ferruginous and Swainson's Hawks

Abstract

Raptors are an important component of prairie ecosystems. I examined the effects of grassland conversion to agricultural fields on densities of nesting prairie hawks. Densities of Swainson's hawks were recorded for comparison. The 2 species of congeneric hawks responded differently to habitat loss despite considerable overlap in their use of resources. As cultivation on study plots increased, ferruginous hawks declined. Swainson's hawks were more abundant in areas of moderate cultivation than in grassland or in areas of extensive cultivation. Differences in the hawks' responses were attributed to differences in their ecology, primarily prey utilization. There was no evidence that soil quality affected hawk abundance.