Saw a water dish for birds that had an all weather light socket in a bowl underneath it, and a 40 watt bulb in there.
Would look in cutaway view something like this:
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/~O \
I stopped at the feed store earlier to check on getting a defroster for the birdbath. The birds and squirrels all depend on it, and it was frozen solid this morning. I went out and added some warm water, but that didn't last too long before freezing again. The problem with the defrosters is needing electricity, and I don't have an outdoor outlet. I've never checked to see if I have one in the shed, but I don't think so. I'm wondering if they make them that are battery powered. There is so little need for it here. It just doesn't get below freezing that much.