I've searched this forum pretty thoroughly and read all the posts about chickens not roosting in their hen house. So let me begin by clarifying the following (as it will probably answer most of your initial questions):
- All are exactly a year old and have been laying for a while.
- All have been happily trotting into the hen house at night - all through last summer, fall, and winter.
- I have thoroughly checked the hen house for mites, as well as the birds. No signs whatsoever.
- The hen house does not have a light.
- The perches they are trying to roost on are located inside the run, but outside the hen house sleeping area. They are higher than the perches inside the hen house.
- There is hardware cloth buried 3 feet out around the entire coop and run, so no predators have been inside.
- The hen house has good ventilation.
So... why would they all be trying to roost inside the run at night, rather than going in the hen house portion? They are not trying to roost anywhere outside... always in the run portion.
Photos of coop are below.