If you want to keep separate chicken flocks, you may end up with one flock on one side of the farm and another flock on the other side. Or in the same barn, but separated by a wall. In this case, the chickens (most notably the roosters) will hear each other day in and day out, but not see one another. Will this be stressful for the chickens? I can imagine that a rooster that constantly hears another rooster will start thinking "oh, get off my land or come and challenge me already!", while a rooster that hears hens will go "why won't you come to me when I'm crowing for you? Get over here, you need my protection and wonderful semen!" I guess hens would be more laid-back, but I don't find it a stretch that even they might find it disturbing. When I ponder chicken psychology questions, I tend to think "what would it be like for wild chickens?" And I assume that wild chickens would often hear chickens from other flocks that they can't see, living in thick vegetation and all. However, maybe it's an unnatural situation to hear it day in and day out? Thoughts, comments and experiences, my friends?
I don't think it stresses them. I have roosters crowing on opposite sides of the property and they can hear roosters up the road both directions. The ones on my property usually free range, they keep to their own flocks and rarely confront one another.
Hens though in Hen only Focks might be coaxed by a Roosters calls to come to join his flock....Down the road from me we hear a Rooster too...Lester crows back sometimes to the other Rooster...
Game roosters it would definitely bother, but just normal chickens no it doesn't stress them. Several flocks within earshot and the only interaction with any of them the hens were also within sight.
I can tell you the first thing my flock does when ever they are let out to free range: They immediately run to the grow out coop. Sometimes there are chicks there, sometimes cockerels. Currently, there is one lonely cockerel who is waiting for processing day. Without fail, the flock runs to that grow out coop to visit with who-ever is in there. And after processing, Jack will run to that grow out coop, and do a thorough inspection until he's sure there's no one there. In a large enough free range situation, I'm guessing each roo will keep his little harem out of the range of other roos. From what I see, there is a fair amount of communication between my grow out flock, and my main flock, especially when it comes to predator alert.
I have a group of 6 week old chicks in one room of my barn and week old's in another - Today I noticed when the smaller chicks go chirp crazy at feed time the older birds get rowdy and super vocal. My interpretation was these were feed calls