As you can see, perfectly normal. That’s pure pecking order in action. For whatever reason certain spots on the roosts are considered prime real estate and the highest ranked birds claim them. They can be pretty vicious in enforcing those rights. Something else I sometimes see is that they don’t always want certain chickens roosting next to them. Sometimes a higher ranking hen will peck a lower ranked hen just for trying to sleep next to her, even when she already has the better spot. Other than when I have some going through adolescence, roost time is pretty much the only time I see much evidence of the pecking order, as far as violence goes.
I read that to say you have two separate roosts, each 2.2 meters long? I’m always a proponent of giving them as much space as you reasonably can, but I’m not a great believer in specific numbers for that space. This is for coop and run square feet, roost length, brooder space, nest size or number, basically anything related to chickens and space. I’m more into quality of that space which is a lot harder to define. There are a lot of different variables that go into that quality: flock make-up and size, your climate, your management techniques, the personality of your individual chickens and total flock dynamics, and just so many other things. I understand people starting out need guidelines but don’t start thinking that any specific number is perfect for you. They can be good starting points but you need to remain observant and flexible. Adjust if you need to. If that’s two roosts that is a lot.
Your roosts are different than most in that your chickens can step up to them, they don’t have to fly to mount the roosts. When they are on the roosts and settled in, chickens don’t take up much room. But they need to get up there. Some people have to have that extra room for flying chickens with wings spread.
Most of the minimum recommendations on here are for roosts to be 30 cm from the wall and any other roosts be separated by another 30 cm. That will physically give them enough room to fit. That’s what I do. But the quality goes up if they are separated by a bit more. If you happen to have one that likes to peck at other weaker chickens around it, more separation can help with that. Sometimes the weaker needs to be able to get away from the stronger. What I often see on my roosts is that the stronger are on the front roost on the end next to the window, prime real estate. The weaker are at the far end, usually on the back roost, as far away as they can get. The ones in the middle of the pecking order are in the middle.
The maturity level of those two new hens can have a big effect on roost requirements. If they are mature and old enough to lay, they will probably force their way into the pecking order somewhere. It may get a little messy but they will probably work their way in.
If they are not yet mature hens but immature pullets, the entire scenario changes. Mature hens automatically outrank immature pullets and can be really vicious in enforcing their pecking order rights. The new pullets will probably form their own sub-flock and avoid the older hens as much as they can. As long as they have enough room during the day to avoid having to stay close to the older hens your integration will probably go OK.
But if your roosts are set up so they cannot avoid the older hens it’s really normal for my juveniles to sleep somewhere other than the roosts. They don’t like getting beat up. Like Aart, I have a juvenile roost set up, lower than my main roosts and horizontally separated and higher than my nests. This gives my juveniles a safe place to go that is not my nests. Don’t be surprised if your two new ones don’t immediately sleep on your main roosts with the others. Once they work their way into the pecking order, they will.
I envision your climate as it is possible you might get to freezing occasionally but it’s pretty rare. You probably have a lot of heat in the summer. And you have rain. I don’t have that climate but a lot of people that do like open air coops. You can find some examples in the “coops” tab at the top of this page. That could be anything from where only one wall is wire to where all four walls are wire but you have a section you keep dry for nests and roosting, plus wind protection on the roosts.
One issue with those can be keeping the coop floor dry. If the coop (or run for that matter) stays wet it can become unhealthy. If you have great ventilation so it can dry out and it’s positioned where water drains away from it instead of to it, open air coops normally work out great. If you position any coop (or run) where water drains to it or stands in that area you will probably have a problem no matter which coop you build. I’ll include a link about muddy runs written by a lady that lived in a swamp in Canada. Her conditions were different from yours but she has some good suggestions. The best time to fix a wet coop or run is during the design phase, with location being the most important part.
Pat’s Big Ol' Mud Page (fixing muddy runs):