Introduce new chick/ens to flock issues, and roo trying to breed underage new hen

[Jaymez]

Hi so I'm having issues with introducing my 2 new chicks to the flock. For reference my original flock is made of all silkies and has my roo and hen and then they have 5, 14 week old chicks. So since their chicks are 14 weeks already and I can already see some of them are roos I decided that it was time to start selling them and getting some new hens. Now the original chicks are completely fine with the new ones, but my problem is my hen and roo. So one of the new chicks is a 5 month old white hen, and the other is a hopefully hen and is a bit younger/smaller but I'm not sure by how much and is a grayish color. Now my hen is bullying them but I was expecting that and she's not being overly aggressive, but my problem is the roo. He is about 2 years now and usually is a good boy. When I first introduced him he did his happy, friendly little dance for both of them but I could tell he had his eyes on the 5 month white hen. Anyway after a bit he tried to mate the 5 month white hen aggressively. I can tell that she definitely isn't ready for mating and she's still a lot amount smaller and lighter than him. He didn't even do a dance and he just grabbed her head feathers and tried to hop on. She ran away obviously but he kept holding on and trying a couple more times. He didn't hurt her but he did rip out a good amount of feather but no bald spots. The problem is that I'm not sure what to do from here on. I'm not sure if I should just let them both in the flock and hope he eases up, or of I should keep them separate for now or do something else.

 

[Perris]

I would ensure she has plenty of places to run and hide (lots of clutter in the run if they're not free ranging) and just leave them to work it out. He wants to establish his dominance over her and she's not ready, so there'll be some chasing about for a while, until she's ready and squats for him, so he doesn't have to try to grab her before she takes off.

 

[aart]

Here's some tips about.....
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/