I had a year old hen that had been sort of "keeping to herself" when I let her out of the coop for a few days last week. She'd just peck around for a bit, but then I'd see her just sitting in the corner of the pen by herself. At first I thought she might be sick, but she wasn't exhibiting any symptoms. Then she appeared fine the next day and was out scratchin' with the other chickens. However, when my husband let the birds out this morning, I looked out about an hour later and there she was sitting all alone while all the other birds were back inside the coop. I went outside and put her in the coop & shut the door, but found her dead around 4:30 this evening. It was unbelievably cold here today (high in the teens). Could it simply be that it was just too cold for her??