You can keep pigeons and chickens housed together, but it's best if you didn't. The main reason not to is disease. One that I can think of right this second is Chlamydiosis. It usually presents as a respiratory infection with flu-like symptoms (lethargy, going off food and drink, sunken eyes and dull feathers. Then of course you have all the symptoms that go along with the respiratory part of the disease, cough, mucus, eye and nose drainage, etc. There is no vaccine for this disease but to help keep the chances of it from forming in your flock, you should have a regular worming program in place for all of your birds. And be sure to worm them ALL AT THE SAME TIME. Whether you decide to house them together or not, remember, the choice is yours and you need to do what works best for you. Good Luck !!!