Abstract
I examined spatial relationships between nesting colonies of Great Blue Herons (Ardea herodias) and their aquatic foraging areas by synthesizing data from a survey of nesting colonies, a study of foraging Great Blue Herons, and a wetland inventory. I assessed whether Great Blue Herons gained energetically by nesting colonially at sites central to foraging areas versus solitarily and dispersed evenly over foraging areas.
Nesting colonies (n = 29) were closer to local concentrations of foraging habitat and to Points of minimum aggregate travel to all regional foraging areas than expected by chance. The number of nests per colony correlated positively with the availability of foraging habitat (in hectares) within commuting distance of a colony and negatively with foraging costs (km flown per ha wetland visited). Through computer simulations I found that an equally sized, hypothetical population of solitarily nesting herons dispersed evenly over foraging areas would experience higher foraging costs than colonially nesting herons. The spatial arrangement of wetlands upon the landscape of inland Maine limits the availability of sites with efficient access to heron foraging areas, and favors clumped nesting patterns.