The influence of food availability and habitat structure on nest site selection of the Acadian flycatcher (empidonax virescens)

Abstract

Food availability and habitat characteristics were examined in the vicinity of Acadian Flycatcher nests within a late-successional, Beech-Maple forest during the summer of 1999 at the Ravenna Training and Logistics Site in Portage County, Ohio. Flight interception (window) traps were placed at nest sites, non-nest sites, and upland sites to monitor the distribution of arthropods. Specimens were collected on a weekly basis, counted, sized and identified to family. Habitat characteristics were also measured at nest sites and non-nest sites. For all arthropods combined, the quantity and quality ofinsects was significantly higher in riparian habitats in comparison to upland habitats, and was higher at nest sites than at non-nest sites, although not significantly. Ofthe 19 most abundant taxonomic groups of arthropods, Halictidae (Halictid bees), Apidae (bumblebees), Conopidae (thickheaded flies), Araneae (spiders), and Phoridae (scuttle flies) exhibited significantly greater mean abundances at nest sites than at upland sites. These results suggest that the distribution ofinsects in the forest plot I studied is not random. A higher abundance of Diptera and Hymenoptera, may enhance the quality ofhabitat for Acadian Flycatchers. Nest sites tended to have a lower tree density, with subsequently less coverage of leaflitter than non-nest sites. This allowed for an open air space surrounding the nest. An open space surrounding the nest facilitates aggressive nest monitoring and defense behavior, which is common in flycatchers.