I have 10 Rhode Island Reds now 22 weeks old, full grown and producing eggs well. It's now getting cold at night in the Virginia mountains and the chickens would rather roost tightly together on a perch I have set up in their run than go into the coop with a heatlamp. When I first turn the lamp on, they go inside to investigate but then eventually sleep on their perch. At what temp do you really worry about their well being? and has anyone ever seen this? Is there a way to coach them into the warmer coop?