I have been watching the pecking order business in chickens for a good many years now and most of my observations involved games.
Following refers to birds of the same social group. Chicks under direction of hens appear to have a relatively stable social arrangement that seldom involves overt aggression. It is often hard to tell who is boss. When chicks are not hen raised, then pecking order is easy to figure out. With juveniles it appears to be a frequently changing arrangement, especially where males are concerned. Shortly after weaning (hen ceases to cluck) cockerels typically have a powerful bout of fighting. If adult rooster is not around, the fighting can be serious enough that heavily involved cockerels will be too tired / sore to make roost on following night. Cockerels will have another round at about the same time they begin the first molt into adult feathers and again adult rooster seams to suppress how far such fights go even though he may not get directly involved. A final go around takes place at about time cockerels are in complete adult feathers (bull stag). With my red jungle fowl x American games this is time cockerels disperse from natal group. With pure games, cockerels / stags must be isolated from each other from that point on. Pullets tend to be much less volatile as a whole.
Mature birds in breeding groups / harems (1 rooster and 1 to 10 hens) have very stable pecking orders. Rooster is at top and once pecking order is established, it is stable among hens for entire breeding season. Rank among hens appears stable over multiple breeding seasons so long as membership does not change at top of order.
Between social groups, usual pecking order issues do not always apply. The social groups, not individuals, are what hold territories. With adults, larger groups tend to dominate when all else is equal. When birds are not adults, larger individuals tend to dominate smaller individuals from a rival group but occasionally multiple members from a group made of smaller individuals will drive off a single larger individual from rival group. Specific vocalizations are made when a group acts aggressively against an outsider. With my flocks, juvenile groups can operate in the same territory although adult groups generally overlap mostly near water and tend to avoid each other, apparently at direction of roosters. Even game roosters can on occasion operate free range if adequate space is available and birds know each other and their own home range.
What is not clear to me is how birds disperse and setup new social groups. Rank setting amongst hens takes place at this time and roosters appear to be nucleus around which harems form. Therefore hens must be selecting which rooster they will associate with the following breeding season. Roosters appear to be more important in setting up territory boundaries and hens ultimately limit immigration of new hens / pullets into group. New hens seem to have to fight everybody (hens) to see where they will end up in the pecking order.
I have very little experience with hens only arrangements so will defer to others in respect to that.
