Where do ducks mostly find food?

Ducks mostly find food in the pond which is either pond fish or bread sunk from tourists that fed them.

But the duck would have to find food in their habitat as they cant leave the nest out of sight as either if they have eggs a blackbird or a crow will come and eat them. Or if another bird lands in it, the senses will be left in the nest and when the duck comes back the sense of the other bird that was there will be smelt by the other duck and fly off making another nest in a quieter place as they can find.