There is currently an urgent need for climate change mitigation measures. Renewable energy sources, such as wind farms, are important components of such mitigation measures. The Greek Government has set targets for generation of renewable energy. Within this framework, a large part of Thrace (northeastern Greece) has been selected as a Wind Priority Area (WPA 1). It is known, however, that wind farm operation may have important impacts on bird populations, although effects may vary among sites and species. The primary aim of the present study was to determine the effect of wind farms on the mortality of birds of prey in Thrace. The study area is of extreme ornithological value, as the Rhodope and Evros prefectures show the greatest diversity of birds of prey in Greece and one of the richest in Europe, including the last Black Vulture breeding colony in the Balkans. Seven areas that belong to the NATURA 2000 network are either included within or partially overlap with the WPA 1, where the carrying capacity of the area has been established at 480 standard wind turbines (960MW in total). Carcass surveys around the wind turbines were carried out in order to estimate the mortality of birds of prey. The study area comprised 163 wind turbines in operation, 88 of which were monitored on a daily basis. The results of the surveys were corrected for the bias caused by the observers’ detection ability and the scavenger removal activity. Correction factors were obtained through trials performed in previous WWF Greece’s studies . In total, 9 birds of prey as well as 73 other birds and 186 bats were found dead due to collision with a wind turbine. There were differences in bird and bat mortality between wind farms. Following two different mortality equations, estimated and adjusted mortality rates of birds of prey were 0.152 and 0.173 birds per year per turbine. Daily searches have kept the effect of removal by scavengers and humans low. Carcass surveys, if possible on a daily basis, should be carried out at operating and future wind farms in order to monitor bird and bat mortality caused by collisions with wind turbines. It is essential to understand the effect of bird and bat wind turbine-caused mortality on their populations by conducting population viability studies.