Chickens know when to go out in the cold and when to stay in. I have BA's and SLW's. If you have chickens that have a straight comb you need to make sure to take Vaseline and rub their combs with a small layer to coat so they do not get frost bite. Most of the time you want to keep your coops very clean, in the winter, try not to change the bedding to often for some of that layered poop brings out heat to warm the chicks. If you have supplemental light in their coops, you really do not need to add a heating lamp due to a risk of fire. Our BA's don't mind snow as long as there is not more than an inch on the ground. After that they really don't like to go in it. I put old milk crates in their run for them to jump up on to get out of the snow, or a long board to make it easier for me to walk without all the mud. I have done stray/hay/shavings but it would just cause mold if not changed often and could harm your chickens. I also give them scratch to help them keep warm from the corn. I make sure to keep extra feed in their coops for during winter they will eat double the amount, and keep fresh warm water all the time.