I have kept pigeons and chickens together. It isn't really advised, but it can work. Just make sure you keep all your birds healthy, as chickens can pass a lot of stuff to the pigeons (especially worms, eating off the ground as much as they do). Right now I have 3 pairs of pigeons with my ringneck doves, and none of them bother each other. You just have to make sure you have plenty of room, perches, nest boxes, etc. And with chickens, make sure they can't get to the nest boxes of the pigeons. If they fly up there, they could kill the babies or knock the eggs out of the nest. Also, to prevent fighting over food, having more than one feeder is good. I have had doves with chickens, but the doves stayed on their perches above the chickens. They also didn't bother each other. But it depends on the chickens. Some are agressive and some are not.