Having driven past many wind farms, I can certainly say that those blades are not moving any more than 15-25 mph even on a very windy day. Now unless you're talking about tornado/hurricane force winds...
Seriously, they do not turn as fast as you are led to believe by the coal and oil industries.
If you want to find out for sure, drive by a wind farm and look for yourself.
If wind turbines are killing birds, bats included, it is most likely because they are flying into them not being chopped up by the blades like some make it sound.
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Edited:
The speed of a wind turbine is no more than 15-25 rpm not mph.