How long? Some break by themselves after a few weeks. Some stay on and on, running themselves down to nothing. It is impossible to tell how long one will stay on the nest if no chicks are coming.I have a broody BO too, and I don't have a rooster so all eggs are unfertilized. I don't have a cage to put her in to break her. How long will she brood if I let nature run it's course?