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Put the heat at only one end and keep it up relatively high and well secured. Don't just rely on the clamp. Monitor the birds behaviors. If they are going back and forth between the heat source and their food and water peeping, that's fine. If they're distressed chirping then they're cold. If they're laying around panting they're overheated.
Hello! Welcome to BYC! Great advice has been given! X2 on radiant heaters! I use brooder plates they work well and can be adjusted easily! Good luck with your birds!
I have used a heat lamp but make sure it is secure ( I applied extra clamps) and put an old screen on top of the brooder, so it cannot fall into it.
Also, depending on how many chicks, you can use/make a Mamma Heating Pad/MHP. If you do this, you will want a heating pad that Does Not have an automatic off. You want the heat on all the time when the are young.
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