Thanks JodyJo, I'll turn the lamp off for now. Do you use a heated bowl for water?
I have had -29* here in Colorado...I add NO heat...you truly don't need to...I know its hard to adjust to knowing your girls are in the cold, but as long as they are out of the wind, and have food and water, they need NO heat....I don't use a light either, I want them to have a break and already lost one to egg bound, don't want to deal with this in the winter.
I don't know that I'd just 'turn it off'. If you decide to go with out the lamp, I think I'd go with a much smaller wattage bulb for a week or two first. A sudden 40 degree drop to deal with won't be pleasant, down coat or not.
I have to agree here, now they will have to be weaned off the added heat...keep us posted on how they do!