I will knock on all the wood I can find, we've not had an issue so far in the 2.5 years I've had the ducks. I added 3 last spring to bring the total to 5. So 4 indian runner ducks and 1 welch harlequin duck. They free range during the day, hop in the pond when it starts to get dark until one of us goes out to walk them to bed and lock them up for the night. I'd like to add a few chickens. Ideally not ones I'll be brooding. I was wondering this morning if more critters or adding chickens to the mix would bring more predators or more notice by predators. Then while out raking picker vines out of the garden, the ducks start making noise and flying toward me and their pond. Look up and there is a hawk. Don't see him around often (now I'm not home often much during the day either, but still, don't see the hawk often). Crows kind of chased him away and me by the ducks seemed to be a deterrent as well. Then with how chicken and duck math work... but I don't really see us getting too many.