Despite the colder nights the hen house must still have plenty of ventilation, a build up of condensation in the house can lead to respiratory problems.
An afternoon treat of corn will help them keep warm through the night.
If your birds have restricted ranging, hang greens etc up in their runs, it will keep them entertained and the yolk of their eggs (if you are still getting any this time of year) a deep yellow.
During the winter months I have found the rubber trugs you can buy ideal as drinkers.They can stand up to the coldest of days without cracking and as they are flexible, if they become iced over are easily emptied, a godsend when your fingers are as cold as the water.
Rats can also be a problem during the winter months, removing any feed from the pens overnight and storing the bags of feed in rodent proof containers reduces their chances of a free feed.I keep my bags of feed in plastic dustbins,each hold a 20kg bag of feed and seem sturdy enough to keep mice and rats at bay.