Habitat selection and reproductive ecology among Townsend's warblers (Dendroica townsendi) in southcentral Alaska

Abstract

I investigated habitat selection and reproductive ecology among Townsend's Warblers (Dendroica townsendi) in mature mixed forests near Anchorage, Alaska. I examined selection of territories, nest sites, and foraging sites to identify habitat features associated with each resource. Male pairing and nest survival were monitored to identify factors influencing reproductive success. Females were highly selective for large white spruce (Picea glauca) as nest sites. Foraging behavior varied temporally and was specialized toward medium white spruce early in the breeding season but subsequently generalized across substrates. Territories were heterogeneous in habitat and were characterized by habitat features selected for nesting and foraging, suggesting specific demands for resources influenced choice of territories. Pairing success (98%) and nest success (51%) were generally higher than that of migratory songbirds breeding in forest fragments. Nest predation and blow fly (Protocalliphora) parasitism, factors constraining reproductive output, varied with microhabitat, suggesting that habitat selection may mitigate their effects.