In my flock of 9 in Massachusetts winters I've never really experienced birds showing that they're cold, so to speak. I've been noticing lately though that they are shivering and huddling together in their outdoor run. The winter this year has been warm, normally we experience regular temps at like 20 degrees in January, but today for instance it was 37 degrees. So if my girls are 4-5 years old is this just them experiencing winter in their older and less productive age? Until now they've always disliked winter (they'd stay in the coop rather than walking on the snow), but I'm not sure if is this just them disliking winter more, or if this is exhibition of symptoms of some illness? And what should I do to warm them up a little?