Bird Mortality Associated with Wind Turbines at the Buffalo Ridge Wind Resource Area, Minnesota
Osborn, Robert G., Higgins, Kenneth F., Usgaard, Robert E., Dieter, Charles D., Neiger, Regg D., The American Midland Naturalist
ABSTRACT.-Recent technological advances have made ind power a viable source of alternative energ, production and the number of windplant facilities has increased in the United States. Construction was completed on a 73 turbine. 25 megawatt wind)lant on Buffalo Ridge near Lake Benton, Minnesota in Spring 1994 The number of birds killed at existing windplants in California caused concern about the potential impacts of the Buffalo Ridge facility on the avian community. From April 1994 through Dec. 1995 we searched the Buffalo Ridge windplant site for dead birds. Additionally, we evaluated search efficiency, predator scavenging rates and rate of car(ass decomposition. During 20 mo of monitoring we found 12 dead birds. Collisions with wind turbines were suspected for 8 of the 12 birds. During observer efficiency trials searchers found 78.87 of carcasses. Scavengers removed 39.5% of carcasses during scavenging trials. All carcasses remained recognizable during 7 d decomposition trials. After correction for biases we estimated that approximately 36 +/- 12 birds (<1 dead bird per turbine) were killed at the Buffalo Ridge windplant in I y. Although windplants do not appear to be more detrimental to birds than other man-made structures, proper facility siting is an important first consideration in order to avoid unnecessary fatalities.
Recent improvements in wind turbine technologies have reduced costs associated with wind power production and have generated increased interest in the use of wind energy as an alternative energy source in the United States (Hanson et al., 1992). As a result, wind power companies have recently expanded their programs (Nelson and Curry, 1995). For example, within the U.S., new wind resource areas have been or are being developed in California, Texas and Minnesota and consideration is being given to development in Wyoming, Wisconsin, Washington, Maine, West Virginia and some areas of southern Canada (Nelson and Curry, 1995). Globally, windplants are in operation or under construction in Spain, the United Kingdom, the Netherlands, the Ukraine and Costa Rica (Nelson and Curry, 1995). However, the incidence of bird mortality, particularly raptors, from collisions with wind turbines in California (McCrary et al., 1986; Howell and Noone, 1992; Orloff and Flannery, 1992) has generated concern over the impacts of windplants on avian populations.
Studies of existing windplants in California have shown that the incidence of bird mortality ranged from 0.029-0.117 birds/turbine/year and raptors appeared to be disproportionately susceptible to collisions with these wind turbines (Nelson and Curry, 1995). Orloff and Flannery (1992) suggested that the hunting behavior of certain raptor species may make them prone to collisions. Over a 12 mo period Howell and DiDonato (1991) sampled 359 wind turbines in Alameda and Contra Costa counties, California, and found 42 dead birds. Twenty-five of the 42 were thought to result from turbine strikes and 17 of these 25 were raptors. During 2 y of avian monitoring in the Altamont Pass Wind Resource Area in California, Orloff and Flannery (1992) found 182 dead birds, of which 65% were raptors. They attributed 55% of all raptor deaths within their sample areas to collisions with turbines.
During the fall of 1993 KENETECH Windpower began developing the first 25 megawatt phase of a proposed 425 megawatt windplant on Buffalo Ridge in southwestern Minnesota. To date, few studies on avian/windplant interactions have been conducted outside of California and the potential impacts of the Buffalo Ridge windplant on avian populations were unknown. In Apr. 1994, near the completion of the first phase, KENETECH Windpower contracted with South Dakota State University and the South Dakota Cooperative Fish and Wildlife Research Unit of the National Biological Survey to survey avian populations and activities on the Buffalo Ridge Wind Resource Area (BRWRA) near Lake Benton, Minnesota. …