Mama heating pad thread
Basically is it a cave you make with a wire frame covered with a heating pad that either doesn't have auto shut off or a way to defeat that. Closest thing to a mama hen

Cheaper than a heat plate, can be formed to your specific needs every time you brood chicks and the pad is useful by people when you aren't using it to brood new chicks, which is most of the time for most of us.
Here is the one I used in June 2021 made from a piece of wire shelving.
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and here is where they are when they went out to the barn the next day
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But I don't always have a broody hen at the right time so the kids go out to the barn at ~3 days old with their non mobile Mama. This one was made from a piece of wire fencing
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That is the cave over on the right side. As you can see, the chicks don't need constant heat even in an old, unheated northern Vermont barn in early May. Last frost here, probably like where you are, is about the last day of May. These girls likely never saw ambient temps as high as even 70°F during their first month out in the barn.