Why is my Hen Mounting another hen so often, is it for dominance?

[ChickaChickaChooCho000]

Hey every chicken lover, keeper, enthusiast, etc. I’ve recently encountered something that I’ve never seen happen with any of my other hens before until now. BUT, my white hen who is huge, she sometimes bullies my new blue sapphire gem hen, who is actually so sweet and too nice! I only had the new hen since the first day of this year, so 1/1/21. Right now the white hen, Milky, is a big bully and usually bullies that hen only. It must be a dominance thing right? Cuz obviously they’re both hens so they’re not gonna make babies, unless my white hen turned into a rooster but no, that doesn’t seem to be the case. I’ve heard cases where it’s a dominance thing but I’ve never thought it would be this harsh. She’s the only one who mounts this hen. I wonder if it could be because she’s fighting strongly to keep her position, since she was also one of the new hens back then and had been bullied by the flock, but is now established and maybe she doesn’t want to end up on the bottom again. But my Sapphire Gem hen was so careless about the pecking order it seemed, she was submissive to all of them, she didn’t even try to defend herself. It seems she’s just overly docile haha!

 

[nuthatched]

It's a dominance thing, you're right.
hens don't turn into roosters, that's an old wives tale. They can get male feathers if they have a hormone inbalance.

 

[Allthefloofs]

At the beginning of integrating a bird into our flock one of our established girls would jump on her and grab her neck feathers, much like a male mounting a female. My interpretation was she was teacher the new girl who was boss. She never drew blood, and it was stressful to watch, but it eventually stopped. If it looked like it was really bothering the new girl (she was a rescue so I didn't have a choice in whether she was a single, or I would have introduced two) I separated them for a bit and then let her wander out again with everyone. But that was after two weeks of see-but-no-touch. I didn't put everyone in together from the beginning.