The only time we had a brood of mallards on the pond was before my initial stocker bass were big enough to eat ducklings. They had about 8 littl'uns, to begin with.
The number of ducklings kept dwindling and dwindling. I don't know what got them all, although I know I rescued 4 or 5 from the drain box at one time and later found one dead at the discharge end of the pipe. I think maybe one duckling made it to fledgling status.
It's tough being a baby duck, even with no bass predation.