Ok...trust my broodyMy girl is a super determined broody, I think an EE/cochin mix. The first go round this year, I was worried and took her off the nest every other day and fed her treats to keep her healthy. She didn't lose any weight during her set, and hatched out healthy chicks. The second go round, I let her do her thing, but still gave her food and water every day in the nest. She would get off about every third day when left on her own. Sometimes two days in a row, sometimes went four. At the end/ lock down, she went five days in the nest, with just me giving her water and some chick feed or scrambled eggs. She did not poop in her nest, but she wasn't eating much. Her chicks are now two days old, she has them out and about, and she still didn't lose any weight this hatch. So at least in my (limited) experience, they know what they are doing, and she did just as well when I left her alone. I would make sure your hen is drinking, it is so hot right now. Good luck with your broody girl! They are so much fun, I love watching my hen with her chicks. The funniest thing to me is that her last hatch, 13 weeks, are still in the run/coop with her and the chicks, and are terrified of the babies! So funny, they are almost full grown, but will run from those chicks in a heart beat.
