I’m not sure how the guineas factor into this. I have no direct experience with guineas. They may get involved or may stay out of it, I don’t know. So I’ll ignore them.
Integration usually goes a lot smoother than you usually read about on here. It can turn deadly so you get a lot of advice with an abundance of caution but it is usually not that bad. Since family members have chickens you probably have some experience with them too. That’s another thing that often happens on here, people with absolutely no exposure to chickens see certain behaviors and are ready to call out the National Guard to restore order, while what they are seeing is just normal chicken interaction.
I strongly encourage you to triple that space before you let them intermingle much. My main run is about the size yours will be so I can easily picture it. It’s not as big as it sounds for that many birds. One way chicken have learned to live together is that when there is conflict the weaker runs away or just avoids the stronger bird to start with. They need room to run away but even more important is room to avoid the others.
But room is not just a matter of square feet. The quality of that room is important. That’s where Donrae’s comments are important. Putting things in there to break the line of sight and give them places to hide can help a lot. One common refuge is perches high enough that the stronger can’t peck them from the ground. When I have younger birds in the flock, which is most of the time, it’s pretty common for the younger birds to be on the roosts while the older ones are on the coop floor when I go down there to let them out in the morning. Sometimes they are hiding under my nests which are pretty close to the floor. I’s not quite the same as Azygous’s “safe havens”, they are too close in size, but something of the same idea.
You can never predict with certainty how any living animal will behave, no matter what any of us say someone can come up with an exception. I constantly see exceptions to what I call normal behavior. I’ll still do some predicting.
Mature chickens always outrank immature birds in the pecking order. Notice I’m talking about maturity, not specifically age. That 2-week difference in your younger ones may not work out to be an important maturity difference. Different individual birds mature at different rates. But your 11-month-olds are going to be more mature than your 4 month olds. There is a really high chance your younger birds will instinctively avoid the older ones. If they don’t the older ones may teach them to avoid by pecking when they invade their personal space. It’s possible one of your older birds will go out of her way to attack the younger, but that behavior is pretty rare. But most more-mature birds will peck when their personal space in invaded. But this is one of my exceptions. I often see chicks wandering around intermingling with older hens without a problem, but this is usually after they have been integrated, usually by a broody hen.
What I’d expect is your birds to form at least two different flocks while the younger ones mature. It could be more than two. While your older ones are in the run, the younger may be in the coop, for example. That’s normal behavior.
This is why you need different feeding and watering stations, so the younger ones can eat and drink without challenging the older ones.
I never see immature birds stand up to or fight more mature birds. Maybe some others have but I have not. If the more mature attack they run away or try to hide. If they get trapped where they cannot run away, they hunker down and just take punishment, trying to protect their head. This is where the danger is really high, the attacking ones go for the head because this is where they can do the most damage. You may have seen some old comedies where people keep away from others by running around a table, keeping the table between them and their attacker. This is the kind of things you need to create quality space, things they can run around and get away.
My pullets normally avoid the older hens until they start to lay themselves. That’s when they mature enough to force their way into the main flock and carve out their own place in the pecking order. Sometimes I see this just before they start to lay, sometimes it’s a month after, but generally around when they start to lay. You notice I did into give an age. It’s not age related, it’s maturity related.
You said you have a large coop. How much roost space do you have and how is it set up? The time mine are most brutal to each other is when they are going to bed. Even with an all-mature flock it can get pretty rough when the ones higher in the pecking order kick the lower ranked ones out of the favorite roosting spots. Again it is not inches per bird, it is quality of that roosting space. Some of us have installed separate “juvenile” roosts for lower ranked birds to be able to find a safe place to sleep that is not our nests. Mine is actually over the nests with the top of my nests acting as a droppings board. It’s a little lower than the main roosts and horizontally separated by about 3 feet. Having a coop big enough that you have flexibility to do things like add a juvenile roost or put up a temporary fence or wall to house them separately is a huge bonus.
That’s enough for this morning. Hopefully you will get something useful out of all this. Good luck!
