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Dryad

Prey selection by Chordeiles minor (Common Nighthawks) does not reflect differences in prey availability between breeding and nonbreeding grounds

Stein, Eliza1; Fariña, Nestor2; Villalba, Olga2; Cockle, Kristina L.3; Zubarán, Gastón E.4; Snider, Allison M.1; Baldo, Diego5; Cox, James A.6; Taylor, Sabrina S.1

Published Nov 27, 2024 on Dryad. https://doi.org/10.5061/dryad.q83bk3jsg

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Nov 27, 2024 version files 922.68 KB

Abstract

Predators may adjust their diets to match their energy needs and food availability, but these adjustments have not been explored for migratory aerial insectivores outside of the breeding grounds. We found that Chordeiles minor (the Common Nighthawk), a long-distance migrant and member of the rapidly declining aerial insectivore guild, exhibited similar levels of diet richness, diet diversity, and prey selectivity on the breeding and nonbreeding grounds, despite large differences in prey abundance. We examined the diets and prey communities of C. minor during two breeding seasons in Florida, USA, and two nonbreeding seasons in Corrientes Province, Argentina (2020–2022). We used DNA metabarcoding to identify insect prey in C. minor fecal samples, and we employed malaise and UV light traps to assess the abundance and composition of aerial insect prey communities. The abundance and richness of available prey were significantly higher on the nonbreeding grounds than on the breeding grounds. Even so, C. minor exhibited similar within-sample and within-population diet richness, Shannon and Simpson diversities, and prey preferences at both sites. Adults differed in their consumption of Lepidoptera between sites: adults on the nonbreeding grounds preferred Lepidoptera over all other orders, whereas adults on the breeding grounds consumed Lepidoptera less frequently than expected. We suggest that breeding adult C. minor may deliver Lepidoptera to their young instead of consuming these prey. At both sites, C. minor showed a preference for large-bodied, nutrient-rich prey, suggesting that these generalist predators exhibit less diet flexibility than previously thought and thus may be vulnerable to changes in prey communities at multiple points in the annual cycle.