Ultraviolet Reflectance as a Signal of Individual Quality in Prothonotary Warblers

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The Ohio State University

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The Prothonotary Warbler (Protonotaria citrea) is a Neotropical migratory songbird that breeds in forested wetlands of the eastern United States and winters in the mangroves of Central and South America. Prothonotary Warbler populations have declined by approximately 31 percent in the last 50 years, leading to their listing as a Species of Concern in the U.S.A. Their decline is largely attributed to loss of habitat throughout their entire range; however, the effects of global climate change have also caused disruptions in migration processes, including the timing of arrival to breeding grounds, and first egg date. For many species such as the Prothonotary Warbler, earlier arriving birds are considered “more fit” than other potential mates, as they have the advantage in securing high quality resources. As migration cues are disrupted, understanding different features contributing to mate selection helps us understand what signals of individual fitness may be compensatory for those lost due to anthropogenic factors. This study’s purpose is to provide a foundation for studying plumage as a driver of mate-choice and reproductive output in order to advance research towards understanding the behavioral impacts from climate change on this species. I tested the hypothesis that ultraviolet (UV) reflectance is a signal of individual quality and predict that the brightness of the white patches on tail feathers would positively correlate with arrival date in males, first egg date in females, and fledging success in both. Using tail feather samples and data collected from arrival surveys and nest monitoring of Prothonotary Warblers between 2021-2022 at Hoover Reservoir in Galena, Ohio, I conducted spectrophotometer analysis on 117 feathers for readings on UV reflectance, as well as mean brightness across spectra. Linear mixed-effect models were used to analyze the degree of reflectance against the arrival date, first egg date, and fledging data. The results show no evidence that higher levels of UV reflectance indicate an individual who is “more fit” for males or females. I discuss the implications of this on our understanding of this species and conservation concerns.