Except the species that I would consider aren't indigenous to our area, so I would be helping the native species, so they don't have to compete for resources. And where do you think they would get the duckling I buy at a hatchery from?
Ducks migrate, hatcheries wouldn't get babies from the wild, most birds are protected by the migratory bird act and it's not hunting season. It's illegal. If you do it, I hope you get caught. Buy a duckling from a breeder or hatchery.