Know what you are saying,,,, It will be up to real birds to decide, they can make up their own minds. I have studied about bird houses... the hole size is not correct of the smaller birds, but I have never seen a bird with a tape measure checking... I could easily put dowel in and may,, but, if not the correct size hole, no bird will use it and no cleaning necessary, the bottom I plan on attaching with screws for cleaning,,, I am member of the Audubon Society... but this is probably never going to be hung in a tree.