Rooster bullying a hen

[Sherymaree1]

My rooster is being mean to one of the hens. Pecking her head badly when mating and ran her back into the coop this morning. She is now sitting on eggs inside the coop. Can anyone tell me why he is doing this? Thank you

 

[SwampPrincessChick]

The hen getting picked on is likely the rooster's favorite and he wants to breed her more than the rest. Hens may go broody to hide from the rooster or just stay in the coop to get away from him. I would suggest separating the rooster because it sounds like he is stressing the hen out.