BIRDHOUSE entry holes are being eaten by what?

I have 8 cedar birdhouses in my yard. Recently, after 2 years of hanging peacefully in the trees, I noticed that something has eaten around the holes - openings in them all, obviously something with teeth or a sharp beek. We have mice, squirrels and woodpeckers around here in winter -- any ideas what has done this? I am guessing it was maybe the woodpecker, that they make the hole larger so they can use the box to nest in themselves?|||maybe the woodpecker but more likely the squirrels. you can stop them by cutting a piece of fine wire screen into a square big enough to extend a couple of inches beyond the opening and tacking it on...cut out the middle of course so the opening can be used by birds.|||absolutely positively SQUIRRELS. they seem to like cedar wood especially. They are eating it. another favorite is T11 siding I think its outside layer might be cedar or perhaps the glue is tasty.|||I am wondering if wood peckers nest in houses? We have woodpeckers but I haven't ever seen them at a bird house or a feeder. If woodpeckers did it,it would be for eating bugs and the hole would be almost perfectly round. I would sooner guess squirrels because they make a mess of anything they can find. interesting question!|||Squirrels|||Most likely woodpeckers. I worked at a nature preserve for a long time and experienced the same thing with our bluebird boxes. The woodpeckers are trying to get to the spiders, bees, etc. in and around the wood. As a result, different (larger) species of birds will attempt to nest in your birdhouses.|||mice wouldn't need to make the holes bigger. Squirrels would need to, and they are champion gnawers. They get my vote.|||My guess is either woodpeckers or termites. Just because it's cedar, it doesn't mean that it will repell termites.