This is my first winter with chickens and it has been quite a learning curve (we live outside of Boston). I have 4 lovely Buff Orps who seem pretty unfazed by the winter weather and hang out in their run all day in the bitter cold. A couple of weeks back it was around 0 degrees (F) or below for a few days and I finally turned on a little heater in their coop just in case. For a while I was also putting a thick layer of vaseline on their combs and wattles once a day to protect against frostbite. Despite doing these two things, 2 out of my 4 hens have what I think is the beginnings of frostbite. I'm not sure what to do about it - if anything. Their coop is not insulated, and I have been trying the deep litter method (not sure it is generating any heat though, as it is on a raised wood floor). I keep the coop door closed at night. There is no ammonia smell in the coop, so I don't think there is a lot of moisture in there, but I could be wrong. The litter seems dry enough. Any thoughts? Thanks.