DNA metabarcoding of nestling feces reveals provisioning of aquatic prey and resource partitioning among Neotropical migratory songbirds in a riparian habitat
Riparian habitats are characterized by substantial flows of emergent aquatic insects that cross the stream-forest interface and provide an important source of prey for insectivorous birds. The increased availability of prey arising from aquatic subsidies attracts high densities of Neotropical migratory songbirds that are thought to exploit emergent aquatic insects as a nestling food resource; however, the prey preferences and diets of birds in these communities are only broadly understood. In this study, we utilized DNA metabarcoding to investigate the extent to which three syntopic species of migratory songbirds—Acadian Flycatcher, Louisiana Waterthrush, and Wood Thrush—breeding in Appalachian riparian habitats (Pennsylvania, USA) exploit and partition aquatic prey subsidies as a nestling food resource. Despite substantial differences in adult foraging strategies, nearly every nestling in this study consumed aquatic taxa, suggesting that aquatic subsidies are an important prey resource for Neotropical migrants nesting in riparian habitats. While our results revealed significant interspecific dietary niche divergence, the diets of Acadian Flycatcher and Wood Thrush nestlings were strikingly similar and exhibited significantly more overlap than expected. These results suggest that the dietary niches of Neotropical migrants with divergent foraging strategies may converge due to the opportunistic provisioning of non-limiting prey resources in riparian habitats. In addition to providing the first application of DNA metabarcoding to investigate diet in a community of Neotropical migrants, this study emphasizes the importance of aquatic subsidies in supporting breeding songbirds and improves our understanding of how anthropogenic disturbances to riparian habitats may negatively impact long-term avian conservation.
KeywordsAcadian flycatcher Diet Louisiana waterthrush Resource subsidies Wood thrush
We thank the Carnegie Museum of Natural History, Cokie Lindsay, and Dr. John Wenzel for coordinating access to study sites and providing accommodations at Powdermill Nature Reserve. We thank Eduardo Anaya, Thomas Cordray, Danilo Mejía, Michael Miles, Maria Paulino, and Youstina Seliman for field assistance and the Genomics Facility of the Biotechnology Resource Center at Cornell University (Ithaca, NY) for conducting Illumina sequencing. This research was supported by grants from the American Ornithological Society (formerly the American Ornithologists’ Union), Carnegie Museum of Natural History, National Aviary, and National Science Foundation (DEB-1349870 to Tim Nuttle). We thank the Bayer School of Natural and Environmental Sciences at Duquesne University for supporting undergraduate field technicians through a research fellowship. We thank Powdermill Nature Reserve (Carnegie Museum of Natural History) for supporting B.K.T. through the Rea Research Fellowship and the Bayer School of Natural and Environmental Sciences (Duquesne University) for supporting B.K.T. through a teaching assistantship and the Bayer Graduate Research Fellowship.
Author contribution statement
B.K.T., T.N., B.A.P., and S.C.L. collectively conceived and designed this study as an extension of S.C.L.’s long-term research on Louisiana Waterthrush. B.K.T. and B.D.H. conducted the fieldwork (with guidance from T.N., B.A.P., and S.C.L.); B.K.T. developed the field and laboratory protocols, conducted molecular work (with B.D.H.), performed statistical analyses (with N.L.B.), and wrote the manuscript in the laboratory of B.A.P.
Compliance with ethical standards
All applicable institutional and/or national guidelines for the care and use of animals were followed.
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