Researchers also detected high-density concentrations of birds in forest patches embedded within landscapes that otherwise have very little forest. “The Corn Belt is a habitat desert for these forest birds and they concentrate in forests along the southern edge of that biome before and after making the trek across.” We found that this is acting as an ecological barrier similar to the way that the Sahara Desert in Africa is a barrier to European and African bird migration,” Buler said. “The prairie biome is now dominated by croplands, especially along the Corn Belt that extends into Illinois, Indiana and Ohio. This unexpected discovery is the first recorded evidence of a large man-made barrier to bird migration akin to natural barriers like large water bodies or deserts. act as an ecological barrier, with birds congregating in high densities along the edges. Within these pathways, the study found that the large expanse of croplands in the mid-Western U.S. In the Eastern U.S., songbirds tend to loosely travel along the Mississippi River or along the Appalachian Mountains. Using weather radar data - a technology prized for its utility in comprehensively tracking the nighttime movements of bird populations - the research team found that birds concentrate in certain regions and along certain pathways during migration. Throughout the annual cycle, the migration period is a time when these birds experience the greatest mortality.” “When they’re in these unfamiliar places, they may be more susceptible to things like predation. “Songbirds are often naive about the places that they’re stopping over they don’t necessarily know where the resources are or where the dangers are,” said Jeff Buler, professor of wildlife ecology in UD’s College of Agriculture and Natural Resources. Migrating along a broad front across the continent, these forest-dwelling songbirds often stop wherever they can, making migration a perilous venture. Unlike waterfowl or shorebirds that are heavily dependent on wetlands and coastlines, scientists have not observed strong fidelity to specific stopover sites among songbirds. Successful conservation of migratory bird populations requires enough habitat to be protected at all stages of its annual cycle.” Many of them depend on food and shelter in these forest pockets to complete their migration and a chain is only as strong as its weakest link. “But the entire population moves across the continent twice annually. “Small pockets of deciduous forest are often neglected in conservation planning because birds have low breeding success in these spaces,” said Princeton University doctoral candidate Fengyi Guo, lead author of the study. Now, for the first time, a team of researchers from Princeton University and the University of Delaware has created a comprehensive map of migratory pathways and stopover locations in the Eastern United States. When it’s time for a break in their biannual travels, songbirds descend to rest and refuel, searching for respite in a dwindling number of forest patches.Īvian research often focuses on forests as breeding habitats, but scientists are working to understand the role that small forest patches play in migration - a vital portion of a bird’s lifecycle when you consider that some species spend as much as half the year in transit. When the song pauses in a game of musical chairs, everyone jostles for one of the remaining seats.