About a month ago my ducks one a mallard we have had him for about 5 years. Then I also have a Sweden runner we have had him this will be the 3rd summer. We have always had my dogs. But about a month ago a stray dog come into the yard and tortured our ducks he chased them for about 3 hrs. My Sweden got a broken wing his leg was broken no tail feathers. And the dog took off with my mallard. Now we just have the runner. These past two days the runner will charger full force at the dogs. The older one got pinned in a conner and she got his bill and he bleed a little. How can I stop him. They all have free range. Which my dogs only go out and come right back in. It's soon to be summer and they will enjoy being out. My mallard and the oldest one would always play together so she don't know how to react to the aggressive behavior from the duck. Any advice would be helpful