Okay, he's a bantam, about 5 years old. He has always been very healthy and feisty. He eats layena crumble, grapes, cat food, corn, bread, it varies, there is always crumble. He is cooped with other chickens as well as Guinea Fowl, and is out in a large pen during the day. He started having this problem about 9 days ago. I segregated him to see if he was actually passing stool. He was (with great difficulty), and it was liquidy and smelly. After treating him with yogurt and grapes to eat, soaking his behind, and putting vaseline on it, , he started having normal, greenish, formed stools after about 2 to 3 days. So I put him back out with the rest of the birds. Today he started with the straining to stool again, but now he isn't going at all. And his back end is bulging when he tries, but only brown water comes out, and he appears to be in pain when he does this, (he's making noises when he's straining). I haven't changed his diet at all lately.