Wool hen project! I've eight baby cochin bantams and I've become very leery of heat lamps. Our heating pad broke years ago and they're expensive, otherwise I would make a mama hen brooding pad cave.
So far this is working really well, but I will add more cardboard to the sides for better insulation/less drafts. Basically I took a wool scarf I had knitted, cut it into strips, sewed them onto the thin cardboard of a pasta box, and made the little cave in the corner of their brooder box.
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Last night they were happy next to warm mason jars wrapped in wool, but after the water cools it tends to draw heat away from the chicks so these jars are empty now. I put a baggie of warm rice under the length of wool scarf on the floor of the WH. That taught them quickly that that is where they are to keep warm now.
I absolutely loved getting to tuck them into it like a real hen.

If they continue to be happy with this method I think I will always do it.