I have a couple old bluebird nest boxes which I've ignored for a few years. Yesterday, I was surprised to see a bluebird visit one and return several times, never going in, just peeking in and checking things out I guess. Is it too late to clean out the box? What if it has already started building a nest on top of whatever was in there? I don't want to spook it away by messing with it, but I don't want to discourage future bluebird visits. Any bluebird experts in BYC? Would love your advice! Thanks.