I didn't read through this entire thread, but wanted to give a warning. I've had some very late-born chicks, and yesterday the 3 two month olds suffered frostbite damage on their heads. They seem to be recovering somewhat, thank god, but they left their heads poke out from their henmom that very cold night and I believe both sides of their heads got badly frostbitten. The dummies didn't tuck their heads under wing, which I believe they would have done if they hadn't been getting warmth on their body from being snuggled next to mom. Lesson learned is that they must have a heat lamp when it gets below 35. They're all fine during the day.