It makes the Bacteria and virus more likely. The virus cant live in the cold, add heat and bam they can get sick from that and that is what i mean. So yeah it can make them sick.
They are fine. Get cold hardy birds like humpbacks1962 said. They dont need the heat and really they are better off wihtout it.
If they have some sort of heat then they might not grow the amount of feathers needed for the winter. It would mess them up really. This is just what i think.
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