Dispersal -- Dispersal affects multiple levels of organization, including processes important to population ecology, metapopulation dynamics, speciation, biogeography, and gene flow. Unfortunately, the proximate causes of this important demographic factor are generally not well known. For example, inbreeding avoidance has been suggested as a cause of the sex-biased pattern of dispersal observed for birds and mammals. Although controversy exists as to the importance of inbreeding avoidance, I helped document that meadow voles do avoid breeding with close kin and that dispersal rates in the field are positively related to the degree of kinship within a population. Of course, other factors also influence dispersal rates, and my interest in the proximate causes of dispersal has been incorporated into my studies of habitat fragmentation and community and population dynamics (described above). Additional research into the consequences of dispersal is also warranted, despite the inherent difficulty of studying these relatively rare movements. I believe that technological advances should be incorporated in this field of study. For example, I have used passive integrated transponders (PIT tags) to study the movements of voles, and individual-based models to investigate the movements of cowbirds. Promising new technologies continue to be developed, and I hope to incorporate these in my future research. Finally, I hope to extend my research in this area by investigating the effects of dispersal on ecosystem-level processes. As illustrated by my research of nutrient transport by gizzard shad, the movement of individuals from one location or habitat to another can have strong effects on ecosystem properties such as nutrient dynamics and ecosystem stability. Ecosystem-level consequences of dispersal are not well known, and should provide novel research opportunities.