LANDYS, M.M.; RAMENOFSKY, M.; PIERSMA, T.; WINGFIELD, J.C.: Regulation of Potentially Conflicting Behavior and Physiology during Migration
The avian stage of migration is comprised of distinct sub-stages within which potentially conflicting issues are at work: energy mobilization during flight, versus energy storage during fueling. Therefore, precise control of behavior and physiology during different sub-stages is critical for efficient travel. Corticosterone, the glucocorticoid found in birds, regulates metabolism and feeding, and may participate in the control of migration. I examined the pattern of corticosterone secretion across different migratory sub-stages in a long-distance shorebird migrant. Levels of corticosterone were elevated prior to and during migratory flight as compared to the refueling sub-stage, suggesting that corticosterone may promote behavioral and physiological process typical of departure and flight. Because baseline levels of corticosterone were far below those during capture, I suggest that corticosterone may play a role during migration that is distinct from stress effects. To explore the behavioral role of corticosterone during migration, I experimentally manipulated circulating levels in captive migrants and monitored resulting differences in behavior. Birds with low levels of corticosterone tended to investigate the mudflat and cage floor less than did controls. In addition, birds with low corticosterone titers tended to decrease body mass, even though feeding behaviors were not affected. These results suggest that an elevated level of corticosterone promotes awareness of the environment and assists in the maintenance of the body mass peak typical of departure. On-going studies will verify these data and clarify the physiological role that corticosterone may play during migration.