Wind power and birds

Wind power and birds

I decided to educate myself about wind turbines and birds.  Here is a start.

Wind turbines are designed to achieve a Tip Speed Ratio which maximizes capture of wind energy and reduces tip vortex turbulence (drag).  It appears that a TSR of 4 to 7 is best for three-rotor systems; this means that in a 20 mph wind, the tip speed would be 4 to 7 times the wind speed, or 80 to 140 mph. In a 30 mph wind, the tip speed might range from 120 to 210 mph. Wikipedia says that typical diameters for modern turbines are 180 to 300 feet and most spin at 5 to 20 rpm.  20 rpm on a 300 foot diameter turbine would generate tip speed: (2 ? r = circumference), so c = 942 feet;  20 rpm yields 314 f/sec, or 214 mph.  5 rpm would be only one-quarter of these speeds. I have hit birds with motor vehicles at speeds from 50 to 75 mph; the result is always fatal for the bird.

When we see these big turbines spinning, they look slow.  I have thought that birds would be able to easily see and avoid them, except at night.  I may be wrong in that assumption.