They are living animals. No one can tell you for sure what they will do but in many instances we can tell you what is likely to happen.
With two roosters raised together and kept together without any hens around, they will probably get along great. Just like hens, they will settle who is dominant but it may not be all that violent. It’s also possible it could get really violent, just not likely. Many people keep roosters together in bachelor pens.
If roosters are raised together in the flock with hens, whether there is a dominant rooster in the flock as they are growing up or not, they will all want to be flock master. As the young roosters mature, they well determine which is dominant. Sometimes this gets pretty violent, but a lot of the time this involves skirmishes where neither is injured and quickly changes to running away and chasing. This can be deadly but a lot of the time you don’t even see this behavior going on.
Chickens have developed ways to live together as a flock. A lot of times this involves the weaker running away in a confrontation once they determine they are the weaker. Or they just avoid the stronger to start with. So them having enough room to run away, even when being chased, or enough room to avoid in the first place is important.
Mature chickens always outrank immature chickens. When the immature chickens enter the personal space of the mature chickens, the mature chicken will very often peck the immature. If the immature runs away, things are normally OK. But sometimes the mature really chases with intent to kill. I’d be really nervous about putting those young chicks in with any adults, hens or roosters. Frankly, I just would not do it. You are too likely to wind up with dead chicks.
A very common question on here is when chicks can live with the flock. There is no one right answer. A broody hen will sometimes wean her chicks at four weeks and leave them on their own to get along with the flock. But I’m not a broody hen and I’m not in there 24/7 teaching the other chickens to leave the chicks alone. I think a lot of this answer depends on how much room is available to them so they can run away and avoid. It also depends on how you manage them.
I raise my chicks in the coop with wire between then and the adults from Day 1 so they are recognized as members of the flock. Around 5 weeks I move them to a grow-out coop and run, still next to the adults. At 8 weeks I let the range together in a really big area, but the young ones go back to their own separate coop at night to sleep. I find the most violence with mine takes place on the roosts when they are settling in for the night. I’ve never lost a chick doing this, which means I’m being plenty cautious.
But if yours are not growing up side by side, or if you don’t have lots of room, this can be really risky. It may be a lot better to wait until they grow up to try to mix them. There really is no one right answer to this for everyone.
Then you have the additional issue that you will be introducing chicks to two older bachelors. That does complicate it a bit. I’ve never had a mature dominant flock master rooster harm a chick in any way. I’ve often seen a dominant rooster help a broody with her chicks. Now, non-dominant roosters can be as mean and vicious as hens, but I’ve never seen a dominant rooster behave like that.
You don’t have this situation though. You have two bachelors. If you have young roosters in the flock and they are sexually mature enough for the older rooster or roosters to feel threatened about their position in the flock, they can easily seriously attack the younger roosters. So if that is the case, you probably need to get them introduced before the younger roosters are all that mature. If space is tight, that is really risky, but tight space raises your risks no matter when you do it.
If you have pullets in the new chicks, you have another potential issue. Many adolescent roosters can have the hormones running wild and little self-control. Your two roosters will probably be beyond that stage and probably won’t be over-aggressive sexually with the pullets. But by adding sexually active pullets to the mix, the two older may fight to determine which is dominant. This may involve more chasing and running away or it may get really serious. It’s something to watch for.
If you have only pullets in the young chicks, you can try to add them early before they are sexually attractive. Things will probably work out OK that way. Or you can wait until they are ready to lay. You still have the potential problem with the two older roosters fighting, but that’s going to be a risk anyway. What I’d expect to happen if you mix a flock of pullets of laying age with a mature rooster is that the rooster will immediately start to mate with some pullets to show his dominance and welcome them to his flock. Adding one mature rooster to a flock of hens of laying age is about as peaceful an integration as you can get.
I don’t know enough about your facilities, room, management techniques, sexual make-up of the chicks, or many other things to know how I’d suggest you go about it. I suggest you house them side by side as much as you can and give them as much space as you can when you do allow them to mix.
We integrate new chickens to the flock all the time and usually successfully. They are living animals. No one can tell you what will happen with yours. There is practically always pecking and some fighting involved but it usually works out. Hopefully yours will too. Good luck.
