Honestly, when I had free-range mallards during the winter I adopted several friends who would also eat out of my hands (mine were banded) one particularly bad day duck word must of gotten around becuase I woke to find no less than 50 ducks on my door step. Many were shy but quite a few were very social. They were used to humans feeding them but they were very much wild ducks.
My grandmother once had a very nearly domesticated chimpunk who used to know commands and live under the deck but it was still a wild animal. I would go very, very easy on the feed until you know for sure they are domesticated.
Many states require back toe clipping on domesticated mallards, rouens and wood ducks if you can get close enough to one look to see if it's back toes are intact.
https://www.backyardchickens.com/t/166280/marking-my-wood-ducks-help''
If you see this you can know for sure they are domestic, if you don't then chances are they are wild.