Estimates of bird collision mortality at wind facilities in the contiguous United States

Abstract

Abstract Wind energy has emerged as a promising alternative to fossil fuels, yet the impacts of wind facilities on wildlife remain unclear. Prior studies estimate between 10,000 and 573,000 fatal bird collisions with U.S. wind turbines annually; however, these studies do not differentiate between turbines with a monopole tower and those with a lattice tower, the former of which now comprise the vast majority of all U.S. wind turbines and the latter of which are largely being de-commissioned. We systematically derived an estimate of bird mortality for U.S. monopole turbines by applying inclusion criteria to compiled studies, identifying correlates of mortality, and utilizing a predictive model to estimate mortality along with uncertainty. Despite measures taken to increase analytical rigor, the studies we used may provide a non-random representation of all data; requiring industry reports to be made publicly available would improve understanding of wind energy impacts. Nonetheless, we estimate that between 140,000 and 328,000 (mean = 234,000) birds are killed annually by collisions with monopole turbines in the contiguous U.S. We found support for an increase in mortality with increasing turbine hub height and support for differing mortality rates among regions, with per turbine mortality lowest in the Great Plains. Evaluation of risks to birds is warranted prior to continuing a widespread shift to taller wind turbines. Regional patterns of collision risk, while not obviating the need for species-specific and local-scale assessments, may inform broad-scale decisions about wind facility siting.