My research has centered on the development and use of endogenous markers to trace origins and nutrient allocations in migratory birds. This work involved the pioneering use of naturally occurring stable isotopes, especially deuterium in feathers but has also included trace elements and more recently, compound specific (amino acids, fatty acids) approaches. I have a strong interest in using these tools to establish migratory connectivity and full life cycle conservation of migrant birds throughout the world with a particular emphasis on the Nearctic Neotropical system. These tools have also been applied to tracing investment to reproduction and a new way to evaluate the degree of capital vs. income life history strategies.