New Scientist writes on a report of wind turbines killing bats, two species in particular accounting for 60% of winged animal deaths. The bats lungs are apparently being damaged by the low-pressure region surrounding wind turbine blades.
Though one could trade off the cost-benefit of bat deaths vs general power generation pollution deaths, maybe we need to install ultra-sonic whistles on turbine blades. About 4,000 to 18,000 Hz might work. (and here).