When I added 4 pullets to my remaining chicken, two turned out to be roos. One was rehomed right away, but I thought I'd try and keep the other. One of the pullets bonded tightly to him, but he turned mean to me and was rehomed. She had a total mental breakdown and became mean and really feral. Then we had an accidental hatch of chicks from a nest hidden under a tree, and when the new chicks got big enough to roost, The deranged bird simply drove all the new chicks out of the coop for weeks, They started roosting in the trees. Well one of the hatchlings was a roo and I let him stay and as soon as he figured out what hens fer for, the mental case attached to him. She has mellowed considerably. Before that I had tried all sorts or roosting bar configurations to see if they would roost farther from her, but nothing helped. Finally after weeks of 2 of them roosting in the trees, nasty chicken has mellowed enough and after I chased the tree chickens into the coop a few times and locked them in overnight, they are all roosting in the coop. But that one nasty chicken made everyone's life a misery for quite a while, Now the young rooster mates with her more than with any other chicken, which is fine with me and with her - I guess that's what she needed! You might put a cheap wifi camera in the coop so you can see what the interactions are. That's how I figured out the dynamics here.
