My research program emphasizes the behavior, ecology and conservation of landbird migrants (go here to see a few poster presentations, including those by University of Scranton students) describing our research results. Over half of all landbirds breeding in the United States and Canada migrate to tropical wintering areas in Mexico, Central and South America as well as the islands in the Caribbean. Through the course of their movement, these long-distance migrants travel thousands of kilometers, often through unfamiliar habitats and uncertain weather, stopping at periodic intervals (stopover sites) to rest and rebuild energy stores necessary for fueling a continued migration. Migration is a high-risk, energetically costly event that takes its toll in increased mortality, especially among young, naïve birds of the year. How migrants respond to the energy demand of long-distance flight and cope with contingencies that arise throughout the migratory period is key to their survival and successful reproduction, and constitutes the basic questions behind my research program at The University of Scranton.
We focus on both the spring migratory and breeding periods, (especially as birds approach and arrive at their breeding grounds) as well as evaluating how events during one phase of a bird's annual cycle influence subsequent phases. We use a variety of field and lab techniques to answer questions about the ecology of migratory landbirds. Four questions form the basis of our research:
Transition between phases of the annual cycle: The annual cycle of birds is typically synchronized to segregate the major energy-demanding functions of molt, migration and reproduction. Synchronization of different functions of the annual cycle does not preclude the possibility that events occurring in one phase of the annual cycle influence survival and reproductive success in a subsequent phase. Although we acknowledge this "linkage", convenience and logistics often dictate that we treat each as a discrete unit. How events associated with one phase of a bird's annual cycle influence events in subsequent phases is poorly understood. My research emphasizes this linkage by focusing explicitly on the behavioral ecology and ecophysiology of migrant landbirds upon arrival at the breeding grounds and their subsequent reproductive performance. Recently, we demonstrated that both arrival timing and arrival condition is related to seasonal reproductive performance in American Redstarts (Setophaga ruticilla). We are continuing this work using Gray Catbirds (Dumetella carolinensis) and Common Yellowthroats (Geothlypis trichas), incorporating blood parameters to better estimate arrival condition.
Age- and sex-dependent arrival ecology: The phenomena of differential arrival at the breeding grounds is a commonly observed characteristic of passerine migrants, and is likely to be tightly tied to the phenomena of differential passage during migration; early passage birds likely arrive early at their breeding grounds. Previously we have identified both age- and sex- dependent patterns in arrival of migrants in northern Michigan, which we have related to factors encountered by birds during the preceding migratory period. It is likely that differential arrival reflects a number of factors faced by migrants during both the preceding wintering and migratory periods, including differential strategies played by individuals dependent upon their status (age or sex).
Age- and sex-dependent stopover ecology: Evidence suggests that differential costs of reproduction between sex and age classes, along with intersexual competition, may influence observed migratory patterns and stopover ecology. Our work in northern Michigan identified age and sex specific patterns in passage timing and energetic condition for a number of species of landbirds using the area as a migratory stopover site. Further, we have documented differences in condition, timing of passage and morphology between migrating birds and individuals of the same species that arrived and bred in the area.
Habitat use during migration: Given the extreme energetic requirements of migration, the ability for a migrant to locate suitable habitat to stop, rest and refuel is essential. However, our knowledge of how transients use habitat and what habitat elements (e.g., food, cover) are important during migration is poor. With the assistance of funding from the PA DCNR Wild Resource Conservation Program I continue to study habitat use and the consequences of that use by migrating landbirds through Northeastern Pennsylvania. Go here to see a report on the 2006 field season.
The importance of stopover habitat has been largely overlooked in development of conservation strategies focused on migratory landbirds. We know little about what types of habitat are important during migration, where they occur, or what makes them important. Even less is known about the exigencies faced by migrants as they approach and arrive at their northerly breeding grounds and how these constraints influence an individual's seasonal reproductive success. The existence of a strong migration-breeding season linkage magnifies both the importance of stopover habitat as well as our need to understand what determines en route habitat suitability. My research addresses questions about migrant/habitat relations as well as linkages between phases in the annual cycle.