This means the hen is ready to be a mother. She will sit on the eggs and not eat or drink or poop except maybe once a day. She will turn the eggs with her beak and even help get the chick out of the egg if it needs help. Much better than an incubator.
You can add eggs under her but do it the first couple days. I mark the eggs with an x or the date so if another hen lays eggs in the broody hen’s nest, you can tell which ones to take out.
A couple times, I found that the broody hen will only hatch out a couple eggs and then toss the others out of the nest. Once I took the ones she pushed out and put them in the incubator. One hatched so I gave it back to her and she accepted it. The eggs were cold so I really didn’t think any of them would hatch.
I really worry when my hens go broody weeks after they hatch chicks. My broody hens start laying again when her chicks are about 4 weeks old. The hens can look pitiful if they sit too long. Not enough food and water. So if my hen goes broody again, I take measures to get her UN-broody.
I have tried a couple ways that I read about but there is one that works best. Put the hen in a cage with food and water on the ground. No hay or anything that will make her want to sit. After a couple days, she will give up that urge. If she goes back to the nest to sit, put her back in the cage for awhile longer.
I read you can dunk the hen in cool water to lower her body temperature and it will break her broody cycle. I was amazed at how warm her body felt. I took a five gallon bucket and filled it with water from the outside hose. I dunked her rear end and kept her there for a couple minutes. I did it a couple times. I got wet and the chicken got mad. Don’t care to do that again.