DISSERTATION RESEARCH: The Role of Breeding Hormones in Seasonal Interactions: How Do Birds Meet the Conflicting Demands of Breeding Preparation and Migration?

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Migratory birds complete different stages of their life cycle in locations that can be thousands of miles apart. Conditions during one stage can impose carry-over effects on subsequent stages. It is critical that researchers examine how environmental factors act as carry-over effects across different annual stages in order to fully understand how migratory bird populations are regulated. In the American redstart (Setophaga ruticilla), males wintering in superior quality habitats arrive earlier at the breeding grounds and have greater breeding success than those wintering in poor habitats. While these seasonal interactions are well documented, the underlying mechanisms are not well understood. Energetic demands of spring migration can be compounded by the additional demands of transitioning from the non-breeding to breeding state. This study focuses on how ecological and endogenous factors interact during this transition in Jamaica, West Indies, and if hormones usually associated with breeding can also help migrants reach the breeding grounds earlier. Relationships among environmental conditions, energy stores, breeding preparation, and migration will be examined. Testosterone will be manipulated (enhanced or inhibited, compared to controls) in male redstarts during the period leading up to spring departure. Stable isotope signatures in feathers and/or claws will link wintering ground events with migration distance to the breeding grounds. Breeding readiness and migratory condition will be collected in other Neotropical migrant species wintering in Jamaica. This study will significantly add to our understanding of how wintering and breeding events are linked, and the role of T in a migration context. It will help resource managers develop effective management plans for migratory populations. The study brings together U.S. academic institutions and resource management agencies in Jamaica, and provides many career development experiences (field observations, sample collection, hormone manipulation, laboratory techniques) for graduate and undergraduate students interested in behavioral ecology, eco-physiology, and conservation.