Making the flock as one
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What you are seeing is normal/natural behavior when new birds are introduced into the mix. As time passes they will accept that the new birds are part of the group vs. being "outsiders" that must be driven away to protect the resources of the flock (ie the feed they chase them around). How long has it been since you made the introduction? What process did you use in introducing them? Setting up at least one additional feed station can be a good way to help ease the transition as it short circuits the abilty of the dominate bird(s) to control access to feed by the subordinate birds.