The girls are 10 months old. Their coop is inside a large covered/shaded run that is (so far) predator-proof. All spring and summer at night they roosted on top of the coop and only went inside to lay eggs. Now that it's getting cold, they're still roosting on top of the coop. We are in Georgia so we don't get super cold weather (at worst, nights in the 20s with only a few nights a year into the teens.) We're going to get close to freezing tonight. Should I put a heat lamp in the coop? Or just a low wattage lamp to get them inside? Or leave them alone? I hate to think they don't have sense enough to come in out of the cold!