My 6 pullets are spending all their day inside the tunnel that connects the coop to the run. Can't figure out why they don't spend time elsewhere. Even when I open the run door to free range they come out for a few minutes then head for the tunnel. There are roosts in the run, since taking the pictures on my page, and everything is quite predator proof. Their tunnel is full of poop as we need to build a lid for easier cleaning. Does anyone have any ideas or suggestions? Thanks in advance.