Personally i think that the gains to society from clean power (I KNOW dirty power, we live downwind of a coal fired station, and have an open pit coal mine in our town) far outweigh the deaths of a few bats or birds. Its unfortunate about their deaths, but the technology to prevent it will come soon.
Technology is here right now, nuclear power, its safe, and 99% of all environmental groups agree that this kind of power is the best kind. It is the only power that is clean right now. It can be dirty if not maintained properly.
How clean is power if it is guaranteed to kill animals?
Birds migrate where there is wind, and that is where they want to install wind turbines.