I have a flock of 5 White Rocks and 5 Silver Sebrights that get along very well. I built a separated partition in their coop a few weeks back and put 22 small pullets in it. The little birds had their own door and a separate fenced in area of the run. There have been occasional incursions from one side to the other but nothing major and every time there was no major bickering. So... Last night I took down the fence and allowed both sets of birds to intermingle, The White Rocks could care less. In fact the roosters were quite happy to go dancing around. The only ones who seemed to take any issue were the Sebrights and that wasn't so bad. I couldn't have imagined that it would go so well. Later I will be moving 8 of the pullets into another run with just hens. That is not expected to go well at all. My girls are a mean spirited bunch when it comes to new chickens.