I just moved to the olympic peninsula in Washington state and need to build a new chicken coop. The coop needs to be mobile, so I'm thinking about a tractor style coop. I saw one here in Washington that is entirely open air and am wondering if anyone else has done this!?? It's built like a greenhouse. There's a wood frame on the bottom and rebar arching over it. Over the rebar is heavy plastic and at the front and back is heavy wiring with a door. In the winter, which is very mild here, they put insulating panels over the plastic for added warmth. Apparently they've had it for years and love it. There's no real coop/run distinction. The front and back are open air. The chickens get shade and warmth from the plastic covering it and the entire structure is towed with the tractor every couple weeks to a different part of the farm so that they can graze and fertilize the fields. I'm intrigued! With such a mild climate, do I really need a separate coop/run? My first thought was making sure that they were warm enough and that it would be predator proof, but they haven't had any problems. Their biggest predator problem is with hawks, but apparently the hawk just likes to sit on top of the coop and haven't been able to get at the chickens.