Well, a broody hen will constantly want to set on the nest, and when you approach her, she will act menacing....fluff up her feathers, hiss at you.....some will bite or peck you.....and if you get her off of the nest, she will run around frantically, drink and eat a bit, and then run right back to the nest!
Some don't show all those behaviors and some show some of those behaviors without being broody. Usually it is pretty clear, but some of them seem to go out of their way to confuse you and get your hopes up. I have a Buff Orp that will sometimes spend extra time on the nest, walk around all fluffed up and clucking, and just have a bad attitude in general. She never has gone broody. I never believe a hen is broody until she spends two nights straight on the nest instead of in her normal roosting spot. Then I will trust her with he eggs.
Sorry to jump in on the conversation but I have a new hen that has laid four eggs for me now. The first two I removed and the second two (one of which was laid yesterday, the other last Thursday) I left in the box. She hasn't shown a whole lot of interest in them although I did see her on them late yesterday afternoon. None at all today. But I am a bad parent and I do let her sleep in her nesting box at night and she does. I had read that if they loose chest feathers that it is a sign of them beginning to brood. She has been slightly aggressive with me when I go into the coop but I can't tell how much of that is interest in if I have treats or aggression. How do I know if she is broody enough to hatch these guys? Do I just wait the duration of the 21(ish) days to see if it works? Help!
If your hen has gone broody and will hatch out any eggs, she won't leave the nest except for short breaks. If she isn't showing interest in the eggs and setting on them about 95% of the time, she is not broody and will not hatch them out.