Friends here in Tucson had same problem with woodpeckers on 2 of their elaborately carved wooden doors. They tried all sorts of things - reflectors, stinky things (I guess birds don't care about smell), etc, but nothing worked. He got so pissed off that he put big mouse traps on the doors and caught them by the beaks - and left them for a few days to scare off copy-birds. They haven't had it happen again.