Feather carotenoid content is correlated with reproductive success and provisioning rate in female Prothonotary Warblers

In many avian species, a male's colorful feather ornaments are known to signal individual quality and can serve as the basis for mate choice. Fewer studies have assessed whether this is true for females, who also can display plumage ornaments. We investigated whether breast and crown plumage reflectance in female Prothonotary Warblers (Protonotaria citrea) was correlated with annual reproductive success and nestling provisioning rate. We collected 160 feather samples from 112 nesting female warblers across 5 breeding seasons (2010–2014) in eastern Virginia, USA, and measured their reflectance. Because these data were from a population that was part of a long-term study, we knew the exact age and annual reproductive success of most individuals in all study years. We found a significant positive relationship between crown feather carotenoid content and the number of young fledged, after accounting for the effects of nest initiation date and female age, both of which are known to significantly influence annual reproductive success. There was also some support for an interaction between age and crown feather carotenoid content, such that older females had a stronger relationship between crown carotenoids and reproductive success compared with younger birds. We also had parental provisioning data for some females and found that individuals with higher breast feather carotenoid content provisioned their young more often than females with lower breast feather carotenoid content, and that this was particularly true when males provisioned young less often than average. These results indicate that female plumage is correlated with individual quality and may be used as a signal by males to select higher-quality females. However, more study is needed, and we cannot rule out the role of ornaments in other social contexts such as female–female competition.