Predictors and consequences of diet composition in a declining generalist aerial insectivore
Persistent URL
Author(s)
Uehling, Jennifer J.
Taff, Conor C.
Houtz, Jennifer L.
Allegheny College
Becker, Paige M.
Injaian, Allison S.
Vitousek, Maren N.
Date Issued
June 4, 2026
Abstract
For generalist animals that have a broad range of food choices, the specific diet characteristics that are important for health and fitness are often unclear. Here, we examine whether individual variation in diet composition predicts nestling mass and fledge success, and we identify potential drivers of variation in diet composition, in a declining generalist aerial insectivore, the tree swallow (Tachycineta bicolor). We collected morphological measurements, feces, and fledge success information from adult and nestling swallows. We then used DNA metabarcoding of 429 fecal samples to characterize swallow diets. We focused on two diet characteristics that may be important for generalists: dietary diversity and prevalence of nutritionally important diet items, specifically aquatic insects, which are essential to tree swallows. We predicted that nestlings with more diverse diets that were composed of a higher proportion of aquatic arthropods would be more likely to survive to fledging, and that adults’ phenotypes and their stage in the breeding season would be associated with both their own diets and the diets of their nestlings. Swallow nestling dietary diversity strongly predicted fledge success, but we found no link between dietary aquatic arthropod content and nestling fledging. Adult phenotype did not predict nestling diet, but during the provisioning period, adult females with lower body mass had more diverse diets. Because this study occurred during a single breeding season in one geographic area, future work should further explore the patterns observed here, and especially examine the importance of dietary diversity for wild generalist species across years and localities.
Journal
Oecologia
Citation
Uehling, J.J., Taff, C.C., Houtz, J.L. et al. Predictors and consequences of diet composition in a declining generalist aerial insectivore. Oecologia 208, 77 (2026). https://doi.org/10.1007/s00442-026-05901-w
Publisher
Springer Science and Business Media LLC
Version of Article
Version of Record
DOI
10.1007/s00442-026-05901-w
ISSN
0029-8549
1432-1939
Rights
© The Author(s) 2026. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Type of Publication
Journal Article
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