Perhaps a purely anecdotal story, but...
We did a Elder Hostel birding tour to catch the western European migration through Andalucía and Gibraltar in the fall of 2006. Great birding - we bagged 117 life birds and saw hundreds of eagles. Andalucía is very big in commercial wind farming. We saw several sites with over a 1,000 turbines each. We asked our guides, who were obviously very experienced birders, about turbine kill damage to birds of all types - raptors, passerines, storks, etc. Our guides said that it didn't seem to be much of a problem. Lots of amateur and government types are censusing the wind farms for kills and very few deaths are being reported.
The Andalucian wind farms were in mountainous but open country; typically cattle grazed between the turbines. We didn't ask about bats and don't know much about how they faired.
For what it's worth.
Larry and Mona Rogers