Why would my rooster attack my 15 week old hen?

[shannon84]

I let her out of her coop. I keep a close eye on her to let her see and mingle with other chickens turned my head he attacked her. Not matting either like was being mean! Why?! She's fine and safe now. He isn't even a mean rooster!

 

[nuthatched]

How long has your pullet been in your flock?
How long have you been working on intergeneration?

 

[shannon84]

She's new. I got her Saturday morning. Just started yesterday evening

 

[aart]

She's new. I got her Saturday morning. Just started yesterday evening

OhBoy....
Sounds like a typical reaction to a new bird dropped into the flock.

You might need to read this:
https://www.backyardchickens.com/articles/introducing-a-single-hen-to-an-existing-flock.71997/


And understand these....
Integration Basics:
It's all about territory and resources(space/food/water).
Existing birds will almost always attack new ones to defend their resources.
Understanding chicken behaviors is essential to integrating new birds into your flock.

Confine new birds within sight but physically segregated from older/existing birds for several weeks, so they can see and get used to each other but not physically interact.

In adjacent runs, spread scratch grains along the dividing mesh, best if mesh is just big enough for birds to stick their head thru, so they get used to eating together.

The more space, the better. Birds will peck to establish dominance, the pecked bird needs space to get away. As long as there's no copious blood drawn and/or new bird is not trapped/pinned down and beaten unmercilessly, let them work it out. Every time you interfere or remove new birds, they'll have to start the pecking order thing all over again.

Multiple feed/water stations. Dominance issues are most often carried out over sustenance, more stations lessens the frequency of that issue.

Places for the new birds to hide 'out of line of sight'(but not a dead end trap) and/or up and away from any bully birds. Roosts, pallets or boards leaned up against walls or up on concrete blocks, old chairs tables, branches, logs, stumps out in the run can really help. Lots of diversion and places to 'hide' instead of bare wide open run.

Good ideas for hiding places:
https://www.backyardchickens.com/threads/a-cluttered-run.1323792/