For the past 2 nights, my chickens have not gone up to their roost but rather stayed outside on a perch in their enclosed coop. TUp until this point, they have always gone up for the night. They go up in the morning to visit the nest boxes but have stopped going in at night. What gives? How can I get them to go back up for the night. I have plastic sheeting covering the hardware cloth but its pretty nippy right now in Vermont and Im sure they would be toastier in their roosting area. Any suggestions/ideas are much appreciated.