I started with 4 (4 week old) guineas. I put them in the pen with my 8 week old chickens and everything was fine until the guineas were the same size as the chickens. One of the lavender guineas started picking on the runt chicken to the point she was hiding under other chickens all the time. If I sat in the pen, nothing happened, but as soon as I left and closed the door, the runt would get attacked. This was only one guinea that caused all the problems and I couldn't catch him/her in the act to remove it. I would always loose track of which one it was. I finally built a pen for the guineas and this helped the problem. The guineas and chickens would free range together and seldom had problems. Anyway, 2 of the guineas were taken by hawks in one morning not long ago. I hoped it was the mean one, but I don't think so. That was about 3 or 4 weeks ago, and now the 2 that are left have started being mean to all the hens. I believe I have a female and male.
I just wonder if the one mean one taught the other one to be mean and if I had been able to get rid of the one when it all started, if I would still have a problem. Or would one of the 3 have turned mean. Sorry if that was confusing.
Just wanted to let you know my experience with them and I am not terribly thrilled. I have 4 more keets that are 5 weeks old and I hope they turn out better. I think I am going to keep the 2 remaining juvy's penned up for a while.
If they all get mean, then out with them and I will get another breed of chicken.
Teri