My chicken suddenly became aggressive

[Akhmedov]

Hey guys, i recently started keeping chickens in my backyard. I live alone so i don't think that i need more than 2 chickens. I made a coop by myself and bought my first chicken. Then about 2 weeks later i bought another one. I don't know much about chicken breeds but i'm certain that they're not the same breed. And when i first introduced them to each other the first one(black) started attacking the new flockmate(yellow) but after several days they were okay with each other. It was okay for 6 months but then everything changed about 1 week ago when the black one suddenly started attacking the other one and pecking its head untill bleeding. I seperated them and built another coop for the bully but every night the black one wants to go into her old coop and refuses to sleep in her new one. Can somebody help me solve this problem otherwise i might sell them and i don't want to do that.

 

[sourland]

Do you know what sex your chickens are ? Can you post pictures of them?

 

[rosemarythyme]

Photos of your current set up would help as well.

 

[Akhmedov]

Do you know what sex your chickens are ? Can you post pictures of them?

Sorry for the delay, i was at work. These are the chickens, you can see the lack of feathers on the yellow one's head. I know the coop is a bit messy, but i don't have enough time to clean it properly. As you can see from the photos that i placed some sort of iron bar in the middle of their cage( it was the only thing i could find). I can only attend to their needs when i'm at home. And I ended up discarding the other coop that i made for the black one because she wasn't sleeping in it anyways. But now i have to wake up at 5 am everyday in order to seperate them.

 

[rosemarythyme]

Can you get photos of the set up from further back? It looks really small but maybe that's because the photos only show part of it.