I personally can't believe a bat or a sparrow could be killed by blades spinning at 50-60 rpms, ...
Sure they can. Figure a TSR of 6 or more (for efficiency) and wind speed at the rotor disk of 2/3 the undisturbed wind speed. That puts the tips at four times the wind speed, minimum. Call it 60 MPH in a 15 MPH wind.
(I've generally assumed homebrew wind turbines tended to be designed with a TSR of about 6 rather than, say, 8, to avoid supersonic airflow in a storm. Seems to me increased drag wouldn't be overcoming the increased efficiency by TSR 8, and you can get such a mill start turning before cutin windspeed.)
seems like they would have to fly into them at full speed, then you have to get into the whole thing about the top speed of a common sparrow.......................
Birds are quite capable of knocking themselves out or breaking their necks flying into a picture window. Some examples from personal experience:
- I watched a pigeon in a mall garden kill itself that way when a hawk was chasing it, and there were a dozen or more bird-shaped dust prints on the same windows to indicate this sort of mishap was common.
- When my Nevada place (with a big prow) was under construction, one of the upper panes of the prow windows was broken during installation and the window frame was left open for weeks while the replacement was on its way. One day (when escorting a visiting brother on a Nevada tour) we visited the construction site and found a wild bird had come in through the opening and become confused. I was about to sneak in and opened the sliding door for it to escape, but my brother ignored my instructions to stay clear while I did this and tried to grab the bird. Of course it took off and hit a window pane. This one survived, but it was knocked out for maybe 15 minutes.
One of the problems with the early stealth fighter prototypes was that they tended to be surrounded by dead bats every morning. Hangers in a desert area are popular hangouts for bats. The geometry designed to bounce the radar signal anywhere but back to the radar worked just as well for the bats' sonar. So the bats flew full-speed into the titanium (or whatever) aircraft, with fatal results.
And then there are all the birds hit by cars.
(Of course the animal leftists would be happy to eliminate cars and large glass-sided buildings if it would just save one bird.)