My broody free-range hens generally break off from rest of flock. They also become much quieter and concentrate foraging in the general vicinity of the nest. Another difference is they are much more focused on eating when off the nest and appear to be doing everything at a higher gill. Usually they will be visible off the nest for only a couple hours off the nest each day and that is usually during the middle of the day. I have a broody out foraging like mad right now and shortly she will slip back on the nest. The clucking does not start until the last couple days of incubation and the balling up of feathers is only when she feels threatened by other chickens. The hen I am watching now is probably the quietest hen in the flock excepting for other broody hens.