Often times this is an issue with space. Often times what was enough space for chicks, is not enough space for full grown birds. As Art says, measure.
Sometimes there are just more aggressive birds. Personally, I solve problems for the flock, when you have a very aggressive bird that harasses the other birds, that causes a lot of tension in the flock. Sometimes just reducing your flock by one or two birds, gives everyone enough space and those left get along. Pull the aggressive birds, and see if you like how the flock gets along. If another bird picks on the victim, reverse. Pull the victim, see how the flock gets along.
It is always worthwhile, to try the pulling out of a bird, to see if you can reset the pecking order. Often times there is not a long term change. Then you need to cull a bird or two. A peaceful flock is much more healthy than a flock that is continually stressed.
Mrs K
