Quantifying insect prey preferences of North American breeding birds across mesic and xeric environments

Insects serve as a vital food source for the vast majority of terrestrial bird species, particularly while breeding.  Although this heavy reliance on insects in avian diets has long been acknowledged, many of the basic details about birds’ insect prey preferences remain unknown. Most ornithological references provide only generalized summaries of which arthropods are consumed by birds (e.g., “caterpillars”, “beetles”), rather than species-specific or even family-level identification of prey. Without such essential knowledge, experts are limited in their ability to manage landscapes effectively for avian conservation. To address this deficit, a citizen science project was launched to invite bird enthusiasts and nature photographers to submit photos of birds taking insects to their nests. The birds and insects are identified to species, trophic level, habitat source (terrestrial vs. aquatic) and the feeding records added to a national database of birds’ insect prey preferences, allowing for comparisons across bird species, within bird species, and across geographic areas. Preliminary photo submissions support the hypothesis that birds in more mesic habitats incorporate more herbivorous insects into their diets, whereas birds in more xeric environments rely more heavily on detritivores. Future research will address diet plasticity within species as well as variation in the carotenoid (an essential nutrient for birds) content of various arthropod prey items.