Its been pretty cold here the last few days (lows in the single digits) I was wondering for the chicks well being would it be better to leave them in the coop shut up for warmth or leave the pop door open to the cold and let them come and go out as they please. I,m worried about frostbite on thier combs and so forth. My coop is well ventilated and dry . I,m just concerned. Any advice is appreciated. Thanks