Feather plucking....

Hello all! I have a problem with my chickens bullying each other... I have two coops - one has two 1 year old hens, and the other has one 3 year old hen (the 1st in pecking order) and two 2 year old hens. Peanut, one of the 1 year old hens is constantly bullying Poppy, one of my two year old hens. When I let them out of their coops, Peanut chases Poppy, and I've seen her grab the feathers on Poppy's head. Poppy is missing 1/2 the feathers on her head and neck - no blood, but it looks painful... Should I just give Peanut away (I do know someone who only has 1 chicken and is looking for another, and she's just as crazy about chickens as I am), or is there something else I can do?

Thanks!

 

Does anyone have any ideas?

 

The problem is that this behavior has been going on for months- how long does it usually take for them to establish things? Also, I'm pretty attached to Peanut because she is sweet to people, just not Poppy.