I kept my breeders over winter and all are fine, without losses. We have had -13 here, I have them in a 3 sided building in cages. I only raise coturnix tho. Most important thing is making sure fresh water is available, those temps are a real pain. I take water out after dark, and replace it every few hours in the daylight. I am retired so am home most days. If I can't be here, my DDs watch over my birds.