Taking care of Hens as a pet sitter, some people use warming lights but this should only be done for babies or adolescence chickens. The hens “roost” on a ledge within the coop, they huddle together to keep warm. Put wood shavings on the floor of the coop about 2 inches thick, as that breaks down along with the bird’s poop, it will keep the birds warm. Use a heater to keep their water liquid, they will drink a lot of water during the winter. Also keep the water clean. Corn feeding in later afternoon will keep the hens warm. Most of all keep the hens in a secure coop with outside access so predators cannot make a snack from your flock.