Oh yea, I forgot about the hawks.
I don't worry too much about the hawks around here. I did lose a very small duck to a hawk but my Muscovy are as big if not bigger than the hawks. A hawk did attack one of my females but quickly gave up and flew away as the female Muscovy simply returned, unharmed to her grazing with the other ducks. We also have a bunch of crows around and the tend to chase the hawks away.
I do worry about several eagles that nest close by but, so far, they don't seem to have any interest in my ducks. I figure if the were going to go after my ducks, they would have done it in the couple of years I've had the ducks here.
I do take extra precautions with ducklings but rat snakes are my problem when they are young. Easily remedied with a little rat wire.