For the site selection of wind power pllants it is decisive from a species protection point of view whether the risk of bat fatalities will increase significantly. A substantial ban by Art. 12(1) lit. a council directive 92/43/EEC cannot even be avoided implementing CEF measures. Numerous investigations show that bats are active in the height area of rotor blades and might be killed. But so far only few authors have investigated bat activities in different heights.
The study presented has been carried out over two nights using a helium balloon. Automatically recording batcorders registed the bat calls syncronously in three different heights. The results show that bat activities in the height of the rotor blades significantly differ from activities close to the ground or even to the height of the forest canopy. The species mapped on the height of the rotor blades (Pipistrellus pipistrellus, P. nathusii, P. pygmaeus, Vespertillio murinus) usually feed in the open air space.