Something that I feel I should ask the question as to "why"?
We have many birdboxes in the garden, one in particular that was on a shed when we bought our house in 1983, and all have fixed lids.
The 1983 birdbox has never been cleaned and every year there is a family of bluetits. Our white box, an addition a few years ago, ditto.
Without birdboxes they would nest in hollows in trees and other natural places and there is no one to clean these nests, I think they must do a natural "spring clean" for themselves.
So why do we clean birdboxes ???
1983 box
2010 box (I think ::))
Ninnys