I agree that most studies I have seen show that bird mortality rates due to windfarms are usually not statistically significant.
There is currently concern over bats - not only at the farm I mentioned previously, but at many facilities around the country. Seems the bats are actually attracted to the wind farms for some reason, and when they get close, their lungs explode. So the problem becomes simply to figure out why the bats are drawn to the area and try to prevent it.