DISSERTATION RESEARCH: Hormonal Regulation of Avian Biparental Care

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Parental care is an important component of reproduction that is observed in a diverse range of animals and is especially common in birds. The neural and hormonal basis of avian parental care is not well understood, especially in the many birds where young are raised by both mothers and fathers working together. The hormone prolactin has a well-established role in maternal care in mammals, and so prolactin and its brain receptors are a promising candidate mechanism of parental care to investigate in birds. The goal of this research is to experimentally test for a causal role of prolactin in promoting the onset of parental behavior in a biparental songbird, the zebra finch. This research will provide new insight into the mechanisms of avian parental care, allowing the integration of this important group into the comparative framework that will provide the predictive power for understanding how these mechanisms may function and evolve in other animals, including humans. The project will contribute to the scientific training of undergraduates, including women and underrepresented minorities. Additionally, the results will be promptly published in journals accessed by a broad audience of researchers, presented at national meetings, and disseminated to the public through a website and outreach programs for middle school girls. The researchers determined that circulating prolactin (PRL) is significantly higher in zebra finches (Taeniopygia guttata) during late incubation and early post-hatching care compared to other times in the breeding cycle. To test the hypothesis that PRL plays a causal role in promoting the onset of parental behavior, they will perform two experiments testing the effect of suppressing the normal peak in PRL during late stage incubation in breeding birds, and experimentally increasing PRL in paired, but non-breeding, birds given foster chicks. Parental behavior will be recorded in the nests with small video cameras. To confirm that the treatments have the predicted effect on PRL concentrations, plasma will be assayed before and after treatment using a validated ELISA. On the last day of treatment brains will be collected to determine the effect on central PRL-mediated cell signaling via the PRL receptor using immunohistochemistry. All recordings and data in digital form will be archived at Cornell University to allow public access using the archiving services of the CU Library.