Bald eagle and golden eagle mortalities at wind energy facilities in the contiguous United States

The Raptor Research Foundation|Joel E. Pagel, Kevin J. Kritz, Brian A. Millsap, Robert K. Murphy, Eric L. Kershner, and Scott Covington|September 13, 2013
USAImpact on Birds

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. This paper attempts to quantify the number of eagles killed at wind sited other than the large project at Altamont Pass California which is estimated to have slaughtered 75 golden eagles per year from 2005-2007. The summary and conclusions of the paper are provide below. The full paper can be accessed at the links on this page.

Summary and Conclusion

We found a minimum of 85 eagle mortalities at 32 wind energy facilities in 10 states during 1997 through 30 June 2012 (Table 1, Appendix). Sixty-seven (78.8%) of these mortalities occurred during 2008–2012. Six (7.1%) mortalities were of Bald Eagles and 79 (92.9%) were of Golden Eagles. All but one mortality occurred at commercial-scale wind facilities; one dead adult Bald Eagle was discovered under a smaller-scale wind turbine with a blade radius of only 3.5 m. One Wyoming facility accounted for 12 Golden Eagle mortalities, the most for any single facility. Mortality of both species was recorded at two separate facilities in Wyoming. Adults made up 55.5% (20 birds) of the 36 Golden Eagle mortalities for which age class was reported. At APWRA, subadults composed 63.3% of 42 blade-strike mortalities of Golden Eagles (Hunt 2002); however, age class was unknown for more than half (54.4%) of the Golden Eagle mortalities (Appendix), so we could not make a clear comparison.

This summary likely conveys only a limited portion of eagles killed at non-APWRA [Altamont California] wind energy facilities in the contiguous United States, considering the general lack of rigorous monitoring and reporting of eagle mortalities. Thus, our findings of the reported mortalities likely underestimate, perhaps substantially, the number of eagles killed at wind facilities in the United States. Even with this limitation, we report that blade-strike mortality of eagles is geographically widespread in the United States, and both Bald Eagles and Golden Eagles are killed. Given the projected growth in wind resource development in habitat frequented by Bald Eagles and Golden Eagles, estimation of total mortality and better understanding of factors associated with injury and death at wind facilities through robust and peer-reviewed research and monitoring should be a high priority.


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January 24, 2014


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