I have found that for $99 you can get a game camera (used primarily for deer) that will take pictures of whatever is killing your chickens. I had this problem and couldn't determine what it was. I borrowed a neighbors game camera and set it up. One can't comprehend the different animals that lurk at night until you set one up! It makes trapping easier when you know what you're after. If don't want to purchase on of these cameras, do what i did and ask nearby hunters if you can borrow theirs.