I study animal population biology with a special interest in migratory systems. Migratory systems are useful models because conditions experienced at one place and time influence dynamics observed in distant locations; these are systems that link the biology and health of continents. My long-term goal is to understand factors regulating population demography and geographic range distributions, so that we can predict responses to disease epidemics and changes in climate, environmental health, and human land use. I combine fieldwork, lab work and modeling to study these systems and have developed novel statistical tools for determining dietary and geographic histories from chemical and molecular compositions of animal tissues.