Effects of wind-energy facilities on breeding grassland bird distributions
Since 2003, Northern Prairie Wildlife Research Center (NPWRC) has conducted research on the impact of wind-energy development on breeding grassland birds in North Dakota and South Dakota, specifically addressing whether birds are displaced by wind infrastructure. Wind-energy development in the northern Great Plains primarily occurs along the Missouri Coteau and Missouri River Plateau. These geological landforms rank high in wind-energy potential, but they also contain some of the last contiguous blocks of mixed-grass prairie, which is prime habitat for grassland birds. However, the impact of wind-energy development on grassland birds in the northern Great Plains is largely unknown. NPWRC has monitored change in grassland bird densities at three wind facilities and at adjacent reference sites where wind facilities have been proposed but to-date have not been constructed. Due to the availability of pre-development data and data from reference sites, a Before-After-Control (reference)-Impact study design was implemented to examine whether grassland birds exhibit displacement to wind facilities and if so, how far the disturbance zone radiates from turbine infrastructure. We first tested the prediction that overall densities of individual species will change at wind facilities after construction, relative to reference sites. We tested for displacement or attraction during 2 time periods: 1-year post-construction (immediate effect) and the average of 2-5-years post-construction (delayed effect). Secondly, we tested for effects within distance bands of 100, 200, 300, and >300 m from turbines. Our work provides a framework for applying a BACI design to wind displacement studies and highlights the erroneous conclusions that can be made without the benefit of adopting such a design. More broadly, species-specific behaviors can be used to inform management decisions about turbine placement and the potential impact at an individual species level. Additionally, the avoidance distance metrics we provide will facilitate future development of models evaluating impact of wind facilities under differing land-use scenarios.
Jill A Shaffer