Awareness of avian fatalities at large scale wind energy developments first emerged in the late 1980s at the Altamont Pass Wind Resource Area (WRA) in Central California, U.S.A. Observations of dead raptors at the Altamont Pass WRA (Anderson and Estep 1988; Estep 1989) triggered concern on the part of regulatory agencies, environmental/conservation groups, resource agencies, and the wind and electric utility industries.
In addition to the results from the Altamont Pass WRA, other studies and observations have also established that birds die as a result of collisions with wind turbines and related facilities within wind plants. Although fatalities of many bird species have been documented, raptors have received the most attention in California and also in Spain (Anderson and Estep 1988; Estep 1989; Howell and Noone 1992; Orloff and Flannery 1992; Hunt 1994; Luke and Watts 1994; Howell 1995; Martí 1995; Janss, this volume). Other WRA studies have documented deaths of songbirds (Orloff and Flannery 1992; Pearson 1992; Higgins et al. 1995; Winkelman 1995), water birds (Pearson 1992; Winkelman 1995), and bats (Higgins et al. 1995). Generally, these “other birds” have been common species in those areas, not subject to the degree of concern associated with raptor fatalities.
This paper provides preliminary results for a cooperative research project undertaken by the California Energy Commission, the National Renewable Energy Laboratory (NREL), and Western EcoSystems Technology, Inc. (WEST). The project includes studies in the Tehachapi Pass and San Gorgonio Pass WRAs, California. The studies were designed to document bird behavior, bird use, bird fatalities, and bird risk. These were to be determined as a function of turbine size, turbine type, turbine density, wind plant characteristics, and environmental variables within the operating wind plants. These differences can be important in site selection and layout of a new wind plant. The results also provide information that can help developers and regulators estimate effects at new development sites.