The Myth That Wind Farms Are a Guillotine for Birds Is Being Debunked by Hard Data
(www.zmescience.com)
As article says (and IIRC from other sources) it's the offshore turbines that pose the most risk to birds, and mostly to gliding fishing birds (bald eagle, osprey) because they barely see in front of them (they are looking down) and do not expect obstacles on open water.