What are your actual temperatures (windchill only matters to birds out IN the wind, which yours presumably are not -- their shelter needs to have relatively still air, so only the actual thermometer temperature matters). I'm surprised it'd be getting down much below freezing in Alabama yet, although I confess I have not been glued to the weather channel.
If you are SURE it's frostbite not pecking, I'd be concerned about humidity or draftiness. Although, if they *have* started to get frostbite for whatever reason (very large-combed breeds?) then you might consider running a safely-rigged not-too-high-wattage lamp for them to keep them comfortable and keep it from getting worse.
Good luck, have fun,
Pat