BRC-BIO: Determining the neural mechanisms regulating photostimulation of migratory physiology and behavior

This project will allow us to understand how the brains of songbirds use environmental information to time seasonal migrations. Unlike resident species, migratory birds are particularly susceptible to environmental change as they must move through multiple environments each year. They must time migratory journeys without direct knowledge of environmental conditions at their destination, relying on generalized seasonal cues, specifically the seasonal change in day length, photoperiod, to appropriately time departure.

However, we still know very little about the pathways in the brain that process photoperiod information into the complex changes in physiology and behavior necessary to support migration. In particular, the shared reliance of both migration and preparation for reproduction on the same seasonal photoperiod cues has limited our ability to understand how migratory timing is controlled.

This project will use previously identified lighting regimes to isolate migratory physiology from reproduction in order to identify those neural mechanisms specific to migration. By understanding how animals use photoperiod cues to time migration we will be better able to predict the scope of environmental change to which migratory birds can flexibly respond, informing conservation efforts.

This project will create funded research opportunities for multiple undergraduate students to broaden the population of students able to participate in undergraduate research by alleviating the choice between research and a paying job. Building on the equipment and resources developed by this project, a series of public outreach resources on migratory bird physiology and behavior will be developed for use at events both locally and throughout the Alabama Gulf Coast community.

The project was jointly funded by the BRC BIO program and the Established Program to Stimulate Competitive Research (EPSCoR).

This project addresses the fundamental questions of how songbirds detect and integrate photic cues from their environment into the complex array of changes in physiology, morphology, and behavior necessary to support spring migration. Photoperiod changes are well established as a predictive cue controlling migratory timing for many species. However, the mechanisms underlying timing of migration remain obscured.

This is because both seasonal migration and reproduction both rely on increasing spring photoperiod as a cue and require thyroid hormone signaling within the brain to occur. This overlap between migratory and reproductive mechanisms has limited the utility of observational studies that aim to identify neural mechanisms, as well as the efficacy of simple manipulative efforts such as thyroid knockouts.

This project leverages a previously established low intensity green light paradigm to photostimulate the development of vernal migration without triggering reproductive physiology in the well-studied white-crowned sparrow system. The project will then localize neural expression of deep brain photoreceptors capable of detecting this low intensity green light cue by developing custom antibodies for immunohistochemistry.

Then through multi-target in situ hybridization analysis, it will identify migration specific changes in neural thyroid hormones signaling. Finally, the direct role of putative photoreceptor candidates in regulating migratory physiology will be tested by AAV2 viral vector-mediated shRNAi knockdown of opsin expression in the brain followed by stimulation of migration using the green light paradigm.

This work will provide novel insight into the neural mechanisms and the potential plasticity of migratory timing.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.