Rapid increase of onshore wind energy requires more and more land. Sometimes the new wind farms are located in bird sensitive areas. This is also true for some projects prepared for repowering. On the other hand, many wind farms face restrictions in operation due to bird mortality e.g. extended turbine shutdowns in migratory periods.

Wind energy is one of the most ecological energy sources. It is clean, renewable, has low operating costs, is space-efficient. But there are also cons. Fatal collisions between birds and wind turbine blades is one of the most important ones. Research based on field studies, video monitoring, or more recently tracking large birds using transmitters, contributes to social awareness and shows that the problem is serious, especially for endangered species.

This casts a shadow on the image of wind farms as a source of 100% green energy.
The mortality of birds, especially threatened species, has an impact on the conduct of this business. Regulatory offices are introducing new restrictions on the operation of turbines during the bird breeding season, during spring or the autumn migration. Therefore, turbines are stopped for a few, sometimes several weeks per year.