Well, Shadrach [sorry, have no idea which of his many articles I was reading @ the time ~ or if it is merely something I've picked up from his comments] has 3 different large flocks if I remember correctly & his observation is that chickens always prefer to hobnob with their own kind ~ or @ the very least birds of similar size & temperament. From my own observations I would say that is so.
To run a multi~breed flock as many on here do requires a little more patience & just generally keeping an eye on things to ensure the bullies don't get out of hand & the more timid birds aren't terrorised. I believe it
can be done. The birds simply adjust to what is their normal & I believe all my girls have a really good life. If I thought it was a major issue I would change my practise but that being said the favorelles pal up together, the rocks together, the campines together, the Australorps together. The Aussies even recognize the bantam as one of their own but my mutant BR is not recognised as a rock by the other BRs & is ostracised. I have 3 sort of on their own within the flock but they are not bullied or unhappy so I figure I have a win.