Have a small flock of four hens. All are 2-1/2 years old and have been together since birth. Recently three of the hens have "turned" on the fourth and appears they won't be satisfied until she's gone. They will not let her eat or drink in their presence. Any ideas?
This behavior occurs from time to time with no apparent reason for it to occur. Chicken behavior "pecking order" is well developed and difficult to change. The behavior may change back in the future as abruptly as it began.
You can reduce the effects of pecking by trimming beaks (remove about 1/4 of the upper beak on all the birds) which will reduced the damage to the target bird but probably not change the behavior. Adding other feed and water stations will allow all the birds to eat and drink at the same time. It may help to move all the birds to a different location for a period of time so there is no "home ground" for the dominant birds to protect. If you remove the bird, it will be worse when trying to reintroduce the bird to the flock.
This is always a difficult problem to solve with no easy solutions.
Sorry I could not be more helpful, but this is a very complex problem.