Most new chicken keepers worry about their flock when the temperatures drop. The biggest concern is whether or not a heat source should be added.
If you have provided your flock with adequate shelter from the wind and rain or snow, and there’s plenty of hay or straw in their house, I don’t recommend adding a heat source.
The extra things you can do to help your chickens fair the bitter cold is to give them scratch feed before bed and first thing in the morning. This is a hot feed and will help them stay warm, not to mention they love it. If you are worried about frost bite, the best solution is to apply Vaseline to their combs and wattles.
Your chickens will huddle together to stay warm. For peace of mind, stick your hand down between them at night and you’ll be pleased to find they are toasty warm. Chickens are hardy creatures, so my best advice is to not over think the questions involved in caring for them.
Remember, chickens in numbers are warm, and they acclimate rather quickly to temperature changes. If you have young birds that are just out of the brooder, a heat source is necessary until they are fully feathered, usually at about eight weeks of age. Just make sure they have been introduced to the cold and have been given time to acclimate.
Further Reading… Cold Weather Care