I hatched out Barnevelders (dark feathers) and Golden Penciled Hamburgs (yellow with black spots) together 4 weeks ago. I had to separate them early on as the hamburgs are small and the Barnevelders were pecking and pulling at their spots. There was a lot of drama with the little ones squealing alot. No injuries or blood. Initially I separate the brooder with a cardboard & wire window, then had to move to a two brooder system as they got bigger. Last weekend I made them a HUGE brooder out of 2 uhaul wardrobe boxes, and again put the wire window inbetween them. I took out the wire window today. Lordy!! I'm new to this putting chicks/chickens together. I'm sure that of my 5 Barnies, 4 are roos. I have one Golden Cuckoo Maran roo who has been in with the Hamburgs. There was a lot of chest bumping, chasing, flapping.... no injuries and they seem to be working it out. It's funny because you can pretty much tell who are roosters by how they treat each other. Anyway, they are finally all back in the same brooder with no one hurt or getting harrassed. It was a little scary though!!