My Father, who art in Utah, used many methods. He's an engineer. The one that seems to have prevailed is a large size spider that drops down about 6 ft or so when activated by the birds presence or the wind sometimes. Problem with it is that it runs on batteries that don't shut off till it goes all the way back up to the top. So, once the batteries loose power, to the point it does not reach the top, it sits there and burns battery power till the batteries leak. So, you have to be around to look for it. Can't leave property for 6 months. Also, he found out that if he lets the magpie population be around they seem to keep the woodpeckers away. He found the devise by searching (spider woodpecker).