Predictors and consequences of diet variation in a declining generalist aerial insectivore

In this study, we examined the predictors and fitness consequences of tree swallow diet variation. We collected fecal samples from breeding tree swallows in Ithaca, NY, USA and performed DNA metabarcoding using the COI gene to identify arthropods in the feces. Using sequencing results, we then identified dietary diversity and aquatic insect content (a proxy for highly unsaturated fatty acid content, an important macronutrient for tree swallows). We examined the consequences of diet variation for tree swallow fitness and fitness-related traits, and we explored predictors of diet variation (phenotypic traits, breeding stage, age, sex, and nest box site).