I had to rehome half of my first guinea Flock at 3 mo when they started going after the chicks and ducks... They were amazing. The guinea flock would separate out a victim like a wolf pack separating a single deer. Then the flock would pile on top of the victim, ripping out feathers while it screamed and the other birds scattered. I don’t know how they picked their victims: it was like payback for any that had bullied them in the brooder, so ducks and cockerels. They would act ok with the rest, but became terrified of the guineas. The attack was impressive, coordinated, scary, and fast. I rehomed the aggressive ones, which turned out to be almost all of the males.Thanks for all of the great information. I really wish that there was more complete information online about all of the behaviors. The information I found when entertaining the idea was basically raise the keets with the chicks if you want them to go into the coop at night. We initially wanted the Guinea to take care of a tick problem. Got the chicks too since that is what we read about. Now we love the chicks and are at the end of the rope with the Guineas. (Well one Guinea in particular)