A few weeks ago, I acquired 6 hens from a hen and added them to my flock of 4 hens and a rooster. My original birds all hatched out together and never had any social problems (fighting). I introduced the new ones gradually and there were no problems. They free range all day, from an hour or two after sun-up to sun-down and are locked in the hen-house at night. The day before yesterday, I had to leave them inside slightly longer than usual. When I released them, two or my original hens started fighting. I left them at it, assuming they had to work out a new peck order, but they realy went at it, for a long time, despite it being clear who was winning. I finally separated them when it looked like real injury might result. I left the weaker hen ("the black one") in a cage but with the other birds all day yesterday and put her back on the roost after dark last night. I let them out first thing this morning. When I went out to check on things, shortly after they emerged, the "black one" was hiding behind the henhouse and her opponent ("the brown one") was fighting with the other, third, old hen. This went on and on with the Black One, making noise behind the henhouse. After a lot of noise, I swear the Black One started to crow! It was a noise unlike any I've heard from a hen and it really sounded like a full-fledged crow! She laid an egg yesterday too, in the isolation cage, so I know it was hers. I removed the Third Hen. After a while the Black One emerged and started fighting with the Brown One again. I've now got the Brown One in isolation, the Black One is parading outside the cage, and the Third Hen is staying out of the way. Has anyone had this experience? What about the crowing? Any advice on how to stop the fighting before they really hurt each other? I had a brief conversation with a vet friend who mentioned that sudden extremely aggressive fighting could be a sign of a tumor affecting estrogen or testosterone production. But what about that egg?? I really don't want to have to take care of separate flocks (or an isolated hen). Please help! Many thanks!!