This study evaluates the impact on birds of prey of nine wind farms in Thrace, where a large scale wind farm development project of at least 960 MW is under development. The study area is located in the prefectures of Evros and Rhodope in Thrace, northeastern Greece and it is widely known for its high ornithological value. The “Near threatened” Black Vultures reproduce a few kilometers to the southeast of the area and they use it for foraging. This is currently the only Black Vulture population left in Southeast Europe. The area is also considered as the last stronghold of the “Endangered” Egyptian Vulture in Greece, with very important premigratory concentrations while it hosts the most important Golden Eagle breeding population in Greece. Approximately 50% of the wind farm development project area is covered by Natura 2000 sites. Carcass surveys around a selection of wind turbines in the study area were carried out by WWF Greece to estimate bird mortality. Results of the surveys were corrected for bias caused by the observers’ detection ability and the scavenger removal activity. Trials to estimate the bias were performed. In addition, surveys of spatial use by birds were carried out. Indices of avian space use were then calculated and comparisons made between a previous monitoring study run by WWF Greece in 2004- 2005 and this study (hereafter also referred as “first monitoring period” and “second monitoring period” respectively).