Wind power is among the fastest growing alternative energy sources and the mid-Atlantic region of North America is a primary focus for wind power development. Although considered a “green” energy source, wind energy can have negative impacts on wildlife, especially birds of prey. Threats to breeding and wintering raptors from wind turbines have been extensively studied in several areas but there has been little work on impacts of turbines on migratory individuals.
We are evaluating conflict potential between migratory raptors and wind energy development in the central Appalachian region of eastern North America. Our study takes place at two spatial scales and focuses on rare golden eagles as an umbrella species for soaring raptors. At a continental level, we are tracking and modeling eagle movements in the context of broad scale topographic and weather conditions to understand the determinants of flight behavior and thus, broad-scale scenarios where birds and turbines may interact. At a local level, we are using high-frequency GSM telemetry to measure how eagles respond to micro-site slope, elevation, habitat and meteorological features. We are analyzing these data to understand the conditions when eagles and turbines are most likely to interact and how eagles may respond behaviorally to the presence of turbines.
Results/Conclusions
Energy minimization models show that eagles should track “leading lines” when migrating through the Appalachian region from summer breeding areas to wintering grounds, particularly when thermals are weak. Migratory pathways of tracked birds show high fidelity to tracks predicted by models. Birds move in a broad front through the Appalachian Plateau in New York and Pennsylvania and show age specific patterns of behavior in this region. However, both tracks and models show large numbers of eagles of all ages passing through a bottleneck in the ridges of south-central Pennsylvania. Tracked birds in this bottleneck region spent less time in thermals and flew more quickly and more directly than when they were outside of this region. Similarly, within the bottleneck region, eagle flight uses orographic lift, placing them relatively closer to the rotor swept zone.
Wind energy development risks impacting birds of prey throughout the annual cycle. Although migration is the shortest period of that cycle, because landscape features can concentrate birds into restricted areas, small populations of raptors may be at significant risk during these periods if key concentration area are developed without attention to bird behavior.