Conclusions
We tested one of the predictions of the “stress-mediated egg rejection” hypothesis, which predicts that hosts should mount physiological stress response when they perceive cues of brood parasitism. Our results are partially consistent with this prediction: while we show that POMC expression is elevated in birds exposed to non-mimetic eggs compared to mimetic eggs two hours after experimental parasitism, plasma corticosterone levels did not differ between the treatments at this timepoint, and experimental parasitism with non-mimetic eggs did not affect heart rate. These findings suggest that to understand the applicability and the ecological relevance of stress-mediated egg rejection, we need to address the diversity and subtlety of the stress-response and its effects on behavior in egg rejecter hosts of brood parasites.
Data availability Statement: Data will be made publicly available following the acceptance of this manuscript.
Competing Interests Statement: All authors have no conflicts of interest to declare.
Author Contributions: MA-A, MEH, and DH conceived the study, MA-A and BS conducted the field and laboratory work, GB provided expertise for laboratory work, and MA-A, MP, and MH analyzed data. MA-A wrote the manuscript with extensive input from all co-authors.
Acknowledgements: This research was permitted by institutional (University of Illinois IACUC # 17049), state (Illinois Department of Natural Resources # NH18.6220), and federal (US Fish and Wildlife Service #MB08861A-2) agencies. Funding was provided by the Harley Jones Van Cleave Professorship to MEH, the Katma Award of the American Ornithological Society (to MA-A and MEH), and the LIU-Post summer internship program (to BS and DH). Additional support was provided by the Wissenschaftskolleg zu Berlin, Germany and the Center for Advanced Study at the University of Illinois (to MEH).