Comment on the bottom opening box.. I converted mine to a top opening box so that I could look in and see if everything was okay. I just removed the pivot screws from the top and drilled pilot holes for the bottom. Moved the “lock” to the top and now I can vies the nest, eggs, hatchlings and take photos. Less than 30 minutes. The birds don’t seem to mind one bit, and it is easier to clean after the young have fledged.
David
Stafford, VA