I hatched my first batch of coturnix quail 2 weeks ago. 37 birds out of 60 eggs. Their hutch is in my back garage. I have a pellet stove there. They are on 1/4" hardware cloth in 3 stacked 2x8 ft. pens. Each pen has a 2 ft. section of hay for them to keep warm. With that set-up how cold can it safely get?