In a well-ventilated but not drafty coop, most chickens can stay warm by fluffing up their feathers to trap a layer of warm air against their bodies--as long as they are not wet and or exposed to a draft. Drafts can remove that "jacket" of warmer air surrounding the bird. A coop with poor ventilation allows the buildup of humidity which a major cause of frostbite (it can also lead to the buildup of ammonia fumes, which can make for poor respiratory health since chickens spend more time in the coop during the long nights of winter).
Smaller-bodied or less fluffy breeds may have more trouble maintaining a layer of warm air against their bodies. Large combs and wattles efficiently radiate heat away from the body and are a great characteristic to have in summer, but they can pose a challenge in winter as they may radiate too much heat away and make it difficult for the bird to stay warm. In addition, those large combs and wattles may be more prone to frostbite.
Large-combed birds like this rooster are more susceptible to frostbite and may need additional heat in winter.
The breeds listed in the chart below have some characteristic or combination of characteristics that make them more susceptible to cold. Because of that, they may need some additional heat and/or assistance to help them make it through the coldest part of winter.
*Please note that this list is not exhaustive. Your own flock's needs may vary depending on coop construction, humidity, location of coop, etc. It is important to observe your flock carefully, watching for signs of frostbite or other cold-related problems.
|Bantam breeds that are not especially cold-hardy
|Antwerp Belgian, Belgian Bearded d'Uccle, Booted Bantam, Dutch Bantam, Japanese Bantam, some Sebrights
|Standard-sized breeds having large combs and/or wattles (many are also lightweight)
|Some Andalusian, Catalana, Holland, La Fleche, Leghorn, Minorca, Phoenix, Sicilian Buttercup, White-Faced Black Spanish
|Small-bodied standard-sized breeds
|Fayoumi, Lakenvelder, Penedesenca, Yokohama
|Crested breeds that can get moisture, ice, or snow trapped in their feet, which can make them more susceptible to cold and/or frostbite
|Polish, Crevecoeur, Houdan, Polish, Sultan
|Feather-footed breeds that may get moisture, ice, or snow trapped in their feet, which can make them more susceptible to cold and/or frostbite
|Silkies, Cochin, Brahmas
|Tall, slender, long-bodied breeds
|Malay, Modern Game
|Birds with frizzled, sizzled, or frazzled feather patterns that do not trap heat against the body well
|Can be any breed
|Breeds with roosters having large combs which may be more prone to frostbite
|Andalusian, Campine, Catalana, Dorking, Fayoumi, Holland, Lakenvelder, Leghorn, Maran, Minorca, New Hampshire Red, Norwegian Jaerhon, Old English Game, Orpington, Rhode Island Red, Sussex, Welsummer
Frizzled breeds like this one may need additional heat in winter.
If you determine that your flock needs additional heat to make it through winter safely in your area, it is important to choose use a safe heater, and not a heat lamp, which is a known fire risk.