I've been having a very difficult time figuring out what classifies as "cold" when describing cold hardy birds. We've added two Seabright hens to our small backyard flock and I'm not sure if I need to add anything to our hen house to protect these two little ladies since Seabrights are listed as a breed that isn't "cold hardy". The other breeds in the house are leghorn, EE, barred rock and 2 partridge rock. We don't have a heat source in their house, but there's plenty of bedding and sold walls to block out weather. The two Seabrights tend to sleep under the partridge rocks at night, and all four ladies seem pretty content with this arrangement. We live in NC and our winters are usually pretty mild, we have very few days when the temperature stays below freezing.