There is no doubt that they can dom alot of damage that is for sure. Sometimes they do that to get at bugs but other times? I am not so sure about it. There was one around here that used to go and peck at my next door nieghbors stove pipe. I do not think he was getting any bugs from it but he would still peck on it. Sometimes once a day and other days a couple of times a day. It was very annoying as he did that for most of a summer. He hasn't been around banging on that pipe for a couple of years now though. I still will see one every once in a while though. I just couldn't figure out why it would set there and bang on that stove pipe though..