Effective wildlife conservation requires understanding diet composition and its consequences for population demography. Generalist predators consume a wide range of prey species and are therefore less sensitive to changes in prey abundance than specialists, but their reproductive success can still be driven by a primary prey species. We assessed breeding season diet of an at-risk population of American Goshawks (Accipiter atricapillus) across two ecological zones (coastal and transitional) on the south coast of British Columbia. We used three methods: egested pellets, prey remains, and nest cameras. We further assessed the impact of diet specialization and diet diversity on goshawk productivity. Diet composition and diversity differed among sample sources (pellets, pooled pellets-and-remains, cameras) and between measurements (biomass vs. counts of prey items), highlighting the importance of transparent methodology in raptor diet studies. Goshawks consumed 32 identified prey species but pine squirrels (Tamiasciurus spp.) dominated their diet in both ecological zones (14–61% of biomass), which indicated that pine squirrels may be a primary prey for this population. Diet of coastal zone goshawks contained slightly more birds and fewer hares than diet of transitional zone goshawks, consistent with the hypothesis that goshawk diet reflects local prey abundance. Goshawk pairs at 12 nests monitored with nest cameras fledged 1.4 0.8 young per nest, but we found no evidence to support a correlation between diet diversity or dietary specialization and goshawk productivity. Our results suggest goshawks in this region act as functional specialists on locally abundant prey resources, but more research is needed to understand how variation in prey abundance affects goshawk diet and demographics in this temperate rainforest generalist.

You do not currently have access to this content.