Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Lesley P. Bulluck


Tradeoffs between individual survival and reproductive success associated with aggressive behaviors are a driving force of evolution, but these tradeoffs are often overlooked for aggressive conspecific interactions between females. For avian males, it is well documented that more aggressive individuals tend to provide less parental care. In the few studies that address this in females, the tradeoffs seem to be more context-dependent, varying due to factors such as predation pressure and habitat quality. The relationship between female ornamentation and aggression is similarly understudied, but evidence suggests that both aggression and ornamentation are important traits involved in social selection – the competition for resources other than mates. This study assessed the tradeoffs of female aggression related to parental care and reproductive success within the context of breeding density in the Prothonotary Warbler (Protonotaria citrea), a secondary cavity-nesting warbler that readily uses nest boxes. Breeding density is a proxy for reproductive resource availability in box nesting species. During incubation, we conducted staged nest intruder trials with a female decoy “perched” on the box, paired with playback of female chips, and recorded the focal female’s response. We also examined whether breast and crown feather coloration were correlated with female aggressive response. Our results show that females nesting in high-density environments were less aggressive and provisioned their young more often. We also observed that total nestling provisioning (male and female) was lower in pairs with more aggressive females. Additionally, one female breast feather ornamentation metric (yellow intensity) was negatively associated with aggression regardless of density, while another (carotenoid content) was positively associated with aggression only in high-density environments. Together with previous studies in this system that have found positive relationships between female ornamentation and individual fitness, our results suggest that female ornamentation may provide both inter- and intra-sexual signals and therefore function in both sexual and social selection, respectively. Through explicit consideration of the potential tradeoffs of female aggression, our results also suggest that the costs associated with female competitive traits can be mediated by breeding density.


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