Female ornamentation is correlated with weather conditions during molt in <i>Protonotaria citrea</i> (Prothonotary Warbler): A 13-year study

Abstract Avian species have inspired numerous studies on ornamentation, exploring its role in intra- and intersexual selection as a marker for individual quality. Male birds have been the focus of most studies of plumage coloration despite the fact that females also display ornamentation. Coloration added to feathers during their growth, particularly carotenoid-based pigments, are derived from food resources. As weather patterns affect food availability and abundance, there may be a link between weather conditions during molt and feather coloration the subsequent breeding season. We collected 474 breast feather samples from 329 unique female Protonotaria citrea (Prothonotary Warbler) and 436 crown feather samples from 310 females across 13 years (2010–2023) in eastern Virginia, USA, to assess relationships between temperature and precipitation during molt and breast and crown feather reflectance metrics the following year. We considered conditions in both the breeding and nonbreeding seasons as possible drivers of crown reflectance because at least some feathers are replaced during a previously undescribed limited prealternate molt. Breast and crown violet-blue chroma was lower (therefore higher carotenoid concentration) and breast yellow intensity was higher following cooler and wetter conditions during the late summer molt and not the winter prealternate molt. The negative impact of warmer temperatures on breast yellow intensity was greater in younger females. These results provide insight into how climate conditions affect female plumage coloration, which has previously been linked to reproductive success, and may aid in understanding the impacts of climate change on coloration as an honest signal of individual condition.