I've seen and had pigeons and chickens live together fine, and had bad results start. Chickens by nature are predatory and cannibalistic, they are like cats in that if larger may kill you (I've worked with tigers etc and they can be tame as a puppy but turn on only playing and almost instantly kill you). An injured trapped or sick pigeon can be seen easily as prey in an instant by a chickens instincts. I had chickens that would kill and eat redtail Hawks even by getting their beak into back of neck breaking, eye socket getting eyes and brains etc out, or spurring or clawing at throat and chest.. I've seen these same chickens interact timid even with pigeons in my flocks but know they could easily kill them as they even have Hawks and each other. Point being getting two disabled cats and tossing in pen with pack of established med to large even disabled dogs, would be as bad idea as doing with pigeons and chickens. Supervision during day as have them there would do just fine, and at nite and when not watching going to cage that's 40" squared or close as can have, even hanging against barn/wall large cheap rabbit cage will do for two and two nests to raise babies to fledging for fifty from store at most, or whole roll of wire to use for hundred (if making, the ideal wire spacing I'd inch squared hardware cloth). standards are 36"x30"x16". I've tried 24"squared "standard" breeder pair cages for rabbits pigeons and quail etc and too small to maintain fitness etc, where standard largest size is ideal with nest in each back corner and squared 1"X1" perches half to 3/4 way up perfect for non flying pigeons (like my parlors). Good luck however you do it and keep us updated with pics.
