The regulation of breeding schedules is critical for determining reproductive success, particularly in seasonal environments. This project will determine breeding schedules of two closely related songbirds (the lesser goldfinch and the American goldfinch) to determine how hormones produced and released in specific neurons in the brain are impacted by photoperiod. Gonadotropin releasing hormone (GnRH) stimulates reproductive development, while gonadotropin-inhibitory hormone (GnIH) blocks this development when breeding condiotns are not favorable. This project will compare GnRH and GnIH in these two species as they transition from photosensitive to photostimulated phases during the fine-tuning of reproductive development in relation to local conditions. This project will provide information that will clarify the proximate physiological and molecular mechanisms through which different reproductive schedules in closely related species might arise from simple shifts in the extent to which neural inhibition supresses GnRH release. The project will also provide training for undergraduate and graduate students and will provide unique instruction in field and laboratory techniques.
