I've been having the same problem. Went outside this morning and four of our chickens are dead. A Polish chicken was the first to die, and now the second Polish chicken is dead. These are all from McMurray Hatchery, that we received in August. I don't think it's that they're not hardy enough, as we had problems last winter, too. I have two warming lights in there and their water is on an electric heater. I'm feeding them a combination of layer feed and corn, and we keep the feeder filled at all times, so they can eat when they want.
Our chicken coop is built from old pine, and although we covered up many of the knots and filled in a lot of the spaces between the wood with caulk this summer, it's still a tad drafty.
After reading this thread, I'm convinced it's the drafts that are causing the problem. Today, we're heading to the hardware store to get a couple rolls of heavy-duty plastic and will be wrapping the entire coop in it to eliminate the drafts.
A question -- there is an opening at the top on the east side to allow for ventilation, but I was tired of the sparrows getting in that way. We took some old inner tubes from tires and sliced them and hung them up there to allow for ventilation, without allowing the sparrows in. I'm thinking that should be left alone, the way it is, because otherwise there really won't be any ventilation at all? Your thoughts on that?
Thank you for any help you can provide!
Julie