Many animals migrate during specific periods of the year, moving between wintering and breeding locations. Specifically this research will test the role of overwintering habitat quality in the timing of migration initiation, duration of migration and arrival at the breeding area, as well as ability of Black-and-white-warblers to compensate for the quality of the overwintering habitat while stopping at refugia to refuel during migration. This research will link the timing and distance of migration to subsequent reproductive success during the breeding period and ability to successfully survive the winter using the presence of stable isotopes in feathers and amount of plasma metabolites to quantify an individual's condition. Information about the activity at the stopover areas will allow assessment of the carry-over of nutrients and condition between breeding, migration and overwintering and the integration of all phases of the annual life history cycle. These data will enhance our understanding of how the different phases of an individual's life cycle influence each other. In addition, the project will also provide cross-disciplinary biological training for graduate and undergraduate students from underrepresented groups.
Migration is a fundamental characteristic of the life history of many organisms allowing individuals to take advantage of different habitats as environments change seasonally. Over two-thirds of all landbirds that breed in temperate North America fly thousands of kilometers to nonbreeding areas in Central and South America. Traveling long distances is energetically expensive, and the mortality associated with migration is thought to be substantial. How well a bird solves problems that arise during migration determines the success of migration, and ultimately a bird’s survival. That said, following individuals throughout the year poses a serious challenge, and our understanding of the behavior of birds captured during migration has been constrained by not knowing the bird’s breeding destination, not to mention its point of departure from nonbreeding grounds. We integrated information from stable isotopes (stable carbon and hydrogen isotopes) to geographically link individual birds captured at stopover sites in the southern U.S. during spring migration to the quality of their over-winter habitat and their ultimate breeding destination in North America. Black-and-white warblers (Mniotilta varia) arriving late to the stopover site compared to conspecifics migrating to the same breeding area had stable carbon isotope values indicating that they over-wintered in lower quality habitat such as dry scrub forests. In addition, individuals arriving late to the stopover site were in the poorest condition. These results suggest that over-winter habitat quality strongly influences migration success. Our research is one of the first to integrate information from all phases of a small landbird migrant’s annual cycle to assess the relative strength of carry-over effects among phases. Understanding how the consequences associated with habitat quality on non-breeding, over-winter sites carry-over to affect an individual's success during migration is critical given the growing evidence that the majority of mortality for a migratoary species occurs during migration. This project enhances our understanding of the behavior, ecology, and evolution of intercontinental migratory birds and will further development of conservation strategies for animals whose annual cycle bridge continents. Moreover, the project continued a long history of undergraduate and graduate student traineeship and, because of the dramatic nature of animal migration, provided rich opportunities for outreach to educational groups and the community.
