As previously mentioned, I think the buckshot (I prefer slugs) and electric fencing are your best options. I put up fencing to stop the bobcat attacks that had claimed 6 birds, and knock on wood, I have had no losses since the fence went up. Yes, it limits the chickens and ducks freedom, but in exchange, they don't get eaten! Check out Premier 1 fencing for their net fence. I have 200' attached to the coop, and that gives them a decent sized piece of yard to enjoy. You will want a decent charger for the fence. If I recall, they recommend 1/4 joule output for each section of fence.