Mine were a lot tougher than I thought they'd be. We had a spell where it was -25 with the wind chill but I never added heat and there are only sebrights in their bantam coop. During the worst of the windy days I stapled a feed bag over the ventilation on the prevailing side but left the other sides open. Blocked off two sides of their run but left the rest open. All roosted as they were supposed too and did great. They weren't even adults this past winter but every one of them did great! I'm waiting on eggs now....