I don't know about other duck breeds, but my Khakis are very self-sufficient, spending their days roaming the yard finding things for them to eat. I don't know what they're finding, sometimes they'll be drilling their bills in what seems to be plain dirt, like in a planter pot, and gobbling up SOMEthing tasty. I have 1 drake & 4 hens, and they stay more or less together throughout the day. I have to shoo them into their duck house at night, to keep them safe from overnight predators, and that's when & where they lay their eggs.
I have 4 more ducklings, children of my adult ducks, who are just as wary. I guess I could try to endear myself more by spending time handing them treats. But I don't want to stuff them with bread that they really don't need.
I'm content with things the way they are. We all talk nicely to our ducks whenever we're near, they know we're not a threat, and occasionally we'll have a treat for them. I'd rather they maintain their independence & good survival skills than act like retriever puppies who come running whenever they see me...
...and keep laying those deeeeeeeeelicious eggs!