White-Tailed Eagles (Haliaeetus albicilla) at the Smola Wind-Power Plant, Central Norway, Lack Behavioral Flight Responses to Wind Turbines

Evidence is increasing of bird mortality due to large-scale wind-energy development. Soaring raptors, such as the white-tailed eagle (Haliaeetus albicilla), have proven particularly vulnerable to collisions. In this study, we compared white-tailed eagle flight behavior both inside and outside of the Smola windpower plant on coastal Central Norway. During the eagle breeding period (mid-Mar-end May 2008), we collected data on flight activity (directional flight, social behavior, and soaring) and flight altitude (below, within, and above the rotor-swept zone [RSZ]) at 12 vantage points; 6 within the wind-power plant and 6 outside (control area). We found that white-tailed eagles did not show any clear avoidance flight responses to the wind turbines. Hence, we found no significant differences in the total amount of flight activity within and outside the power-plant area. However, we found less flight activity among adults than among subadults within the power plant compared with the control area. We also found a slightly increased probability of flight activity in the RSZ within the power plant, which obviously may increase the risk of collision with wind turbines. Our findings may help explain the relatively high mortality rate of white-tailed eagles in the windpower- plant area and the recorded peak in eagle fatalities during the breeding season. (C) 2013 The Wildlife Society.