Annie was a little banty - 5 years old - she hasn't been able to fly up to the roost for some months. My roomate was trying to plug in his truck and somehow disconnected the two heat lamps, so little Annie couldn't sit with the other chickens on the roost to warm each other. I found her frozen to death trying to keep three eggs warm. It was heartbreaking - she was so sweet. My favorite, trained chicken Billy (came in the house with me all the time and had been known to dip into my wine) just dropped dead one day - no ryhme or reason. I have a big healthy rooster and two wynodotes and one little banty left. Everyone says not to heat the coop, but it got down to 35 below here and I was so worried about them, I almost brought them in the house. I have not been letting them out of the coop until it warms up to 35.