Open coop?

[Bullitt]

I don't actually have a door between the coop and the run, just an opening in the coop wall. So, my girls decide where to go. Rain, shine, wind, mud, cold, whatever. Then again, I'm not concerned about predators. IMO there's no other reason to routinely confine birds to a coop.

Right. If the chickens are protected in the coop and the run, just allow the chickens to come and go as they please.

In very cold climates it may be necessary to close up the chickens in a coop. I don't know.