My odd hen pecks at the butt of other chickens

[ChickenCluckPoopInUrHands]

She pecks the butt even if they are having a mud bath together.

I provide her with good feed and calcium and everything but this behaviour is still there.

 

[zebular13]

One of my chickens used to peck the other chicken's butts, and I thought she was being a jerk.
Then I read the book "How to speak chicken" and it says that when chickens peck each other's butts, they're often trying to help each other preen. The butt is the one place some chicken's can't quite reach themselves, so they need a friend to help them. The book said that this is typically done by chickens that are lower in the pecking order towards chickens who are higher on the pecking order, perhaps as a way of showing subservience.