COLONY CHOICE IN CLIFF SWALLOWS: EFFECTS OF HETEROGENEITY IN FORAGING HABITAT

Abstract

Abstract One potential determinant of colony size in birds is the local availability of food near a nesting site. Insectivorous Cliff Swallows (Petrochelidon pyrrhonota) in southwestern Nebraska nest in colonies ranging from 2 to over 3,000 nests, but they feed on so many kinds of insects that direct sampling of food resources is impractical. Instead, we investigated the degree to which swallow colony size was correlated with the extent of different habitat types, land use diversity, and plant species diversity in the colony's foraging range, and used those parameters as indices of potential variation among sites in food availability. Amount of flowing and standing water in the foraging range was a significant predictor of mean colony size across years at a site, with larger colonies associated with more water. The same result held for most years when analyzed separately. The extent of flowing water in the foraging range also was a significant predictor of the frequency with which a site was occupied acro...