Well, I haven't gone near my birdbox since May until Monday when I took out the moss which was 'square' from the shape of the box and with a little circular nesting hole! Ah, so cute. There were little bugs in the base so I left the moss on the ground beneath the box. The next day I was going by and about to show OH the remnants of the nest and I noticed 2 almost mummified bodies of baby birds. Aw, how sad.
Maybe I disturbed the nest with my one and only look in and caused their deaths.
Won't do it next year, may get a web cam instead
C