Stopover Biology of Grassland Birds at Restored Tallgrass Prairies
Migration is an energetically expensive but critical part of the annual cycle of migrant birds. Grassland birds are experiencing the greatest population declines of any bird guild, likely because of conversion of grassland habitats to agriculture. Consequently, grassland migrants may have limited options for migration stopover, but few studies have examined stopover biology for grassland birds. In addition, the simple occurrence of birds in grassland fragments during migration periods does not mean that the habitat is providing the food resources necessary for birds to replenish fat stores and continue migration. Through our project, we want to determine what birds are using prairies for stopover and whether these habitats are providing the resources necessary for successful migration. We captured birds by mist-net at Spirit Mound, a 130-ha restored tallgrass prairie in southeastern South Dakota and conducted transect surveys on seven different grassland sites during spring and fall migration periods. We conducted plasma metabolite profiling to determine triglyceride, an indicator of fat deposition, and beta-hydroxybutyrate, an indicator of fat depletion, levels. Preliminary results suggest that grassland, woodland/shrub, and habitat generalist bird species are all present on grasslands during the migration seasons. Moreover, birds are successfully adding fat at this site, suggesting that restored tallgrass prairies can provide high-quality stopover habitat for grassland migrant birds. These findings have implications for creation and management of restored prairie habitats throughout grassland bird migratory pathways.