DNA metabarcoding reveals the diet of Chaetura pelagica (Chimney Swift), a declining aerial insectivore

Avian aerial insectivores have experienced precipitous population declines in recent years which have been largely mirrored by the declines in their arthropod prey. Here, we studied the diet of one declining aerial insectivore species, Chaetura pelagica (Chimney Swift), in Pennsylvania using DNA metabarcoding of fecal and regurgitant samples. We found that C. pelagica most commonly fed on beetles, flies, and true bugs, in addition to mayflies, moths, wasps, caddisflies, and spiders. However, when comparing our barcoding results with prey availability data collected with sticky traps placed lower to the ground near nesting sites, we found that C. pelagica may not feed in proportion to the available prey community; they appeared to avoid some of the most common prey (flies, thrips, wasps, and true bugs), while seeking out some of the more uncommon prey (mayflies and moths). This is the first molecular characterization of the diet of C. pelagica and provides valuable insight into the feeding ecology of this declining species in this part of its range, as well as conservation insights for this species in light of the global trend of decreasing insect biomass.