Bird mortality at wind energy facilities has become the focus of diverse research to understand the causes of collisions and to find methods to reduce and/or eliminate mortality of birds. My study evolved out of 7 years of avian mortality research in the Altamonth Pass and the Montezuma Hills, California. In 1992 Kenetech Windpower began installing their new variable speed wind turbine (KVS-33) with a blade diameter of 33 m. This turbine was designed to replace the older smaller KCS-56 turbine with a blade diameter of 18.5 m. The ratio of the area swept by the hypothesis that the larger KVS-33 wind turbine would potentially kill more birds by sweeping more area than the KCS-56 turbine. I tested the RSA hypothesis by surveying 53 KVS-33 turbines at 3 locations in the Altamont Pass and Montezuma Hills wind energy fields and compared them to randomly selected KCS-56 turbine strings for an RSA that was equivalent. Observers searched areas adjacent to all turbines twice weekly for 18 months. Eighty-five collision mortalities were confirmed during the time when turbines of both types were in operation. The avian mortality ratio between the RSA-equivalent sets of KVS-33 and KCS-56 turbines was 1:3.47. This ration was significantly different than the even ration that would be expected from my experimental design. The evidence does not support the hypothesis that the larger rotor-swept-area of the KVS-33 wind turbines resulted in more mortalities.
Bird Mortality at Rotor Swept Area Equivalents, Altamont Pass and Montezuma Hills, California
Title: Bird Mortality at Rotor Swept Area Equivalents, Altamont Pass and Montezuma Hills, California
January 01, 1997
Journal: Transactions of the Western Section of the Wildlife Society
Howell, J. (1997). Bird Mortality at Rotor Swept Area Equivalents, Altamont Pass and Montezuma Hills, California. Transactions of the Western Section of the Wildlife Society, 33, 24-29.