Why would you add a light? For actual light, or are you talking about a heat lamp? The only reason to add a light for LIGHT is to keep your flock laying through the winter. As your birds won't be reaching laying age until the days start getting longer, I'd not give them a light, unless your coop is very dark and does not have enough windows. If that's the case, I would also ask how much ventilation you have as that's super important year round, including during the winter. I'm in growing zone 4, and my windows stay open as long as the temp is above 20* F. (I also have 16' of soffit vent, ridge vent, eave vents, and a floor level vent.) If you are talking about a heat lamp, please don't give them one. They don't need it. It makes it harder for them to adjust to the winter temps. If the temp stays way below 0* F for days on end, and my birds are hypothermic: decreased activity, decreased appetite, I might give them a bit of heat during the night, but in an average winter, they get no heat.
