I've got a coop with 4 'cauanas in it, two 9m/o layin hens, one 4 m/o hen and one m/o roo. I decided that the 4 younger ones i had in a brooder in the house were ready to go outside into the coop with the other birds. One o' the older layers in broody and on the 2nd floor o' the coop settin'. So that left one layer, one younger hen and the younger roo.I figgered that since there was 4 new birds to introduce that there would be safety in numbers....WRONNNNG !!!! i put the new birds in the coop late evening and sat and wathced for an hour ready to rescure if/when needed. All went pretty well, no more than the usualy chest bumpin to establish order. I figgered all was well and left it at that and went in the house. Next morning all was still well and i left the house for the day. When i got home last evening i had one opf the 4 newbies dead, completely stripped of all feathers but curiously not a mark on it's body(stomped to death?).Two of the remianing 3 had HOLES pecked into the thier backs near their tails and thankfully the 3rd, a white splash had no marks at all on her. I took the 3 back out and filled the holes in the tow o' them with neosporin and put them back in the brooder in the house. Guess i jist gotta wait a few more weeks to re-intorduce these 3. This is the 2nd time i've had 'caunas kill one o' thier own. Why are they so vicious ? My Buff orps are serious about thier peckin order and lettin newbies know thier places but NEVER have they gotten muderous.
How old are the young ones? Once they are the same physical size, they should do ok in hiding. All birds are territorial and if the young birds don't have it in them to hide well enough or make the right motions to show respect, they will get beaten on if they can't get away. A slow intro during free range or during the day for them to get familiar may help out.
My hubby built a small cage for my little ones a couple of years ago. When they were old enough to go out with the grown ups, I took the cage and all. I left them in their little cage with their little heat lamp for a couple of weeks. When I knew they were big enough to not be able to squeeze through the fence that's when I started to let them out to free range with the grownups. And I've never had any more than the occasional squabble. That way they are used to the little ones and the little ones are used to the grownups too. Works out great for me.