I commend you on the idea of not wasting anything, but in this case, I think that city pigeons are probably not the best way to go (or even the prettiest bird to make a sporran out of). I definitely would not eat it (especially if it is dead/dying when you find it) because there are a lot of diseases that birds can die from that can make you sick. If you have to eat it, I would cook the heck out of it until it was beyond well done.