I really don't think it's all about space and available food. I have 20 chickens on 20 acres of both woods and food plots. There are lots of goodies for them to get. Grass hoppers, big ol' fat crickets, baby lizards, seed, frogs, lots of weeds, etc. Besides the chickens' feed troughs, there is a deer feeder they love to take corn and sweet feed from and a compost pile with occasional goodies. The chickens come back every night with full craws (spelling?). Even my best rooster is extremely territorial. If he hears one of the bantam roosters crow, he starts coming over the hills to teach them a lesson. Back when we had turkeys, the big rooster would fight with the tom through the fence.I think it has a great deal to do with the amount of range they have and the total space....easy to avoid birds if they need to do so. I only stock 30 birds to 1 acre and they are never confined to coop unless it's for training purposes or if the snow is too deep for them to want to range out. I don't have a run at all. The pop door is open 24/7 and I have multiple roosts set at different heights and angles. I have plenty of nesting boxes and outside nesting opportunities, multiple dusting areas, hay stacks and apple trees to get up into, etc.
My hens are much too busy shuffling for food in the orchard to give a second's thought to younger birds. The only time they come in contact with them is at the feeder or the roosts..and all my younger birds are smart enough to stay out of the older girls' way.
Maybe it is all about space, available food across a whole acre and hens/roos that are not bored, territorial, or stressed in any way. My chickens are quiet, my roosters don't crow a lot, I never see fighting amongst the hens or roos...I just don't seem to have the issues that others have. I don't have birds all jacked up on high pro feeds or fighting over "treats". I don't know what it is. Must have a Chic-topia, huh?
People have often laughed about my chickens after they drive by and see them roosting in the apple trees or on the swing in the orchard...and even on the sheep's back. I guess they've never seen chickens acting natural and relaxed before.