No apparent trade-off between the quality of nest grown feathers and time spent in the nest in an aerial insectivore, the tree swallow

Life history theory provides a framework for understanding how trade-offs generate negative trait associations. Among nestling birds, time spent in the nest, risk of predation, and lifespan covary, but some associations are only found within species while others are only observed between species. A recent comparative study suggests that allocation trade-offs may be alleviated by disinvestment in ephemeral traits, such as nest-grown feathers, that are quickly replaced. However, direct resource allocation trade-offs cannot be inferred from inter-specific trait-associations without complementary intra-specific studies. Here, we asked whether there is evidence for a within-species allocation trade-off between feather quality and time spent in the nest in tree swallows (Tachycineta bicolor). Consistent with the idea that ephemeral traits are deprioritized, nest-grown feathers had lower barb density than adult feathers. However, despite substantial variation in fledging age among nestlings, there was no evidence for a negative association between time in the nest and feather quality. Furthermore, accounting for differences in resource availability by considering provisioning rate and a nest predation treatment did not reveal a trade-off that was masked by variation in resources. Our results are most consistent with the idea that the inter-specific association between development and feather quality arises from adaptive specialization, rather than from a direct allocation trade-off.Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: 1457251Funding provided by: U.S. Department of AgricultureCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000199Award Number: Funding provided by: Defense Advanced Research Projects AgencyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000185Award Number: D17AP00033Please see the full methods description in the associated publication and the description of column headers in the readme file