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).