If they are raised together from beginning, they just establish it as they grow. You will probably notice one give a peck to another one, and most of the time thats all it is, an occasional peck to say, hey thats my spot. Sometimes when they get older and you introduce new chickens, they can get pretty aggressive. They will chase and peck, and even jump on top of. If they have enough room they can just run away from harm. But its usually not too bad, no more than say, a cat batting at another.
I see my 3 weeks old chicks having little play fights, sizing each other up. My older hens do peck each other occasionally, usually over the treats/kitchen scraps bucket. They peck to say "hey, I claim this good food since I am higher on the pecking order than you" and the lower status hen runs off.
My 28 week old sex-links have a very well established pecking order, and have had for some time. The most obvious time is when they go to roost. If the roosting order is out of synch, there is quite a fuss, untill ever hen is in it's right place. I don't know if the order changes over time or not, but what surprised me the most was that the more mature looking birds (large bright red combs and wattles), are not all further up the pecking order, than the immature looking birds. They are kind of mixed. You will see when the birds go to roost, that the birds on the left side of the roost, (when your facing it) are the birds higher up in the pecking order. If you have a two tier roost, the birds on the lower roost are lower in the pecking order. Darn funny how birds have a social status. It's like Deperate Housewives...
