My 9 week olds (ee, glw, 2 dels, golden campine, pr, wellie) are sleeping in their nest boxes too. some nights I find 5 of them in a single box and have to extract some of them to keep them from overheating. They have a secure coop, and don't seem scared. They just like to be cuddled up together.
None of them seem to want to roost yet, and the poop in the nest boxes is fairly easy to remove each morning (I have shavings in them), so I haven't been insistent or blocked off the nest boxes. It won't be too long and they will be too big to bunk together, I mean 2 or 3 of them are supposed to be fairly large chickens at maturity and the boxes are pretty small (purchased coop, one of the things I questioned at the time -- I'll see if they are large enough when the time comes.
I'll be really interested in seeing the feedback you get on this. You aren't alone, though.
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