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However, if you dont have enough room in your coop, your chickens will fight, and may even become cannibalistic.
Do you have enough feeders and food ALWAYS present in the coop? When chickens become "hungry" it makes them more aggressive.
If then hens are having a dominance squabble, then there isnt really anything you can do about it except watch and make sure they dont hurt one anouther. They will have to settle who is were in the pecking order.
Are they fighting over a laying box? You might want to try just boarding the box up for awhile if that is the case.
However, if one hen is constantly picking on the others, I suggest you remove her from your flock.