Bald Eagle and Golden Eagle Mortalities at Wind Energy Facilities in the Contiguous United States

Eagles are among the bird species that can be injured or killed by collision at wind energy facilities when the birds are flying at the same height above ground as the blades of horizontal-axis wind turbines (Drewitt and Langston 2006). Regions of the United States of America with wind resources adequate for wind energy development (National Renewable Energy Laboratory 2009) often overlap habitats important to Bald Eagles (Haliaeetus leucocephalus; Buehler 2000) and Golden Eagles (Aquila chrysaetos; Kochert et al. 2002). Golden Eagles, in particular, use open spaces and wind resources similar to those valuable for wind energy facilities. High levels of collision mortality are well documented for Golden Eagles at the Altamont Pass Wind Resource Area (APWRA) in California (Smallwood and Thelander 2008, Smallwood and Karas 2009), where published estimates of annual mortality ranged as high as 66.7 to 75.0 Golden Eagles per year in 2005-2007 (Smallwood and Thelander 2008; Drewitt and Langston 2006). Elsewhere, assessments of eagle mortality at commercial-scale and/or private wind energy facilities are either seldom conducted or in some cases not made available for public review. Meanwhile, terrestrial-based commercial wind energy (facilities where electrical power is produced for sale to the local or national power grid) installed in the contiguous United States of America reached an estimated 51 630 megawatts by September 2012, and likely will increase substantially by 2015 (U.S. Department of Energy 2011a, 2011b), suggesting potential for increased interaction between eagles and wind energy facilities. Concerns over the effects of this trend on North America's Bald Eagles and Golden Eagles exist, but are weakly substantiated due to a lack of published documentation of mortalities. Our objective was to summarize documented cases of eagle mortality at wind energy facilities in the contiguous United States of America, excluding APWRA, during the last 15 years, as a starting point for future assessments.