I think it depends on the cat, and on the breed of duck. Call Ducks have to be in more danger than, say, a Muscovy drake! My three cats ignore my ducks. My Muscovy hens have even stolen mice from my smallest cat. Most of the other cats in the area also ignore the ducks. However, there is one sleek black female cat that is far too interested in them. I chase her away when she shows up. My Muscovy hens are believers that the best defense is a good offense, and it works for them. My Rouen just stands still and quacks loudly when threatened. If anyone were to get offed by a cat, it would likely be her! Anyways, I’d be careful, but not paranoid, as someone above me said