An investigation of the use and fitness consequences of using shrub-land habitats by Gray Catbirds (Dumetella carolinensis) migrating through northeastern Pennsylvania

Non-native species are invading and negatively impacting communities throughout North America. Migrating landbirds must find high-quality habitats in which to deposit fat if they are to survive the migratory event, and habitat quality is in large part determined by resource availability. To date, very few studies have examined the consequences of landbirds using non-native vegetation during migration. One way to assess the fitness consequences of en route habitat use is by measuring blood plasma metabolites, in particular triglyceride levels, which indicate fat deposition. This study investigated how habitat vegetation (native vs. non-native), and vegetation phenology influenced habitat use, and plasma metabolite levels in Gray Catbirds (Dumetella carolinensis) migrating through Lackawanna County, Northeastern Pennsylvania in the spring of 2008. One study site was dominated by non-native shrub-land vegetation, while the other study site contained mostly native shrub species. I evaluated habitat use by relating catbird capture rates to percent coverage of the common shrub species surrounding each net (at both sites) and compared plasma triglyceride levels of catbirds captured at my native-dominated site to captures at my non-native dominant site to assess the fitness consequences of using native vs. non-native vegetation during spring migration..