Our 5 chickens (Isa Browns) are about 6 months old. Every evening they put themselves up in the tractor, we close the door until morning. Tonight they did not want to go in the tractor but went into the shed that I put up for their winter shelter. The shed has been up for 3 months and they have not gone in it. It is 56 degrees out tonight so it's not cold. Any ideas why they would change their routine. The tractor is in a fenced 50'x 30' area. It's got grass and a tree in there. They run around and eat bugs but also have layer pellets, oyster shell and grit available. Just curious if anyone else has experienced this.