Several issues

[Cindy in PA]

I always had the best luck putting newcomers on the roost after dark when the others are sleeping. YMMV

 

[ickinom2]

I integrated some ameraucana pullets with my ISA brown hens last summer and the same thing happened at first, so I separated them again. The second time I tried, the older hens pecked my little roo till he had a hole in his head and he died the next day. So I ended up adding a second section to my run with a door in the middle. I put food and water in both sections and kept them seperated for a few days. They were able to be right next to each other through the chicken wire without being able to hurt each other. After 3 - 4 days we opened it all up for all of the to free range and then they all made their way into the coop together that night, and we didn't have any more issues.