Here in Michigan it could be bass, pike, snapping turtles and eagles.

Growing up in Wisconsin with a dad who loved to fish, he always made the same comment when we'd see a duck and her brood swim by the boat: "Muskie's gonna have good eatin'!" and then he'd tell me how he'd actually seen big fish take the little birds from below "like a shark - chomp!" Poor little ducklings!

Don't have eagles but I do have bass and snapping turtles. I thought turtles were vegans.

What kind of land predators are common to your area? Could be something getting to them on land. Knowing your general location would be helpful, you know.

I would put my money on ths snapping turtle. Had the same problem a few years ago and finally had to give up on the ducks and geese because it got so bad.

fed, Seeds, grasses, little snails and other things in water

Around here it is the Herons....

My guesses are Eagles, hawks, herons, shrike, large fish, snakes, coyotes, feral cats, the list goes on and on really.