Abstract

Exotic species invasions are one of the principal problems impacting native species. One of our biggest gaps in knowledge is understanding how native animal species respond behaviorally to exotic invasions. Whether species are able to compensate for the effects of an invasion can give us a clear indication of the ecological integrity of the entire ecosystem. The massive invasion of an Atlantic cordgrass into Pacific salt marshes provides an ideal model system in which to investigate ecosystem wide ramifications of exotic invasions and how animals respond to these changes in their environment. In this study, I will examine how the direct alteration of habitat caused by the cordgrass invasion affects the reproductive, territorial and foraging behavior of song sparrows that reside in the salt marshes of San Francisco Bay. I will also examine other indirect effects of the cordgrass invasion on sparrow populations including new competitive interactions with marsh wrens that are occupying the newly available cordgrass habitat. Results from this study will make significant contributions to our understanding of

1. the potential for invasive species to have complex direct and indirect effects within ecosystems,
2. the ability of species to cope in rapidly changing environments, and
3. behavioral patterns that can be used as indicators if ecological integrity.