I'm just up the mountain in SW Virginia, have a mating pair of Welsh Harlequin ducks and they re wintering just fine without heat in their 4x4x4 coop. I do have a waterer heater that I made from cookie tins that has kept the ice out of the drinking water, but other than that no means of heating. They eat like truckers at a free buffet right now, but they are winterizing themselves.