They've been there for months they said. Others have posted here about ducks being on their lakes for years, so yeah happy not cooped up in a setting unfamiliar to them. Ducks are naturally pretty good foragers, and looks like these are doing just fine. Predators are a concern, sure, but that's nature's way.odd definition of happy. They're vulnerable to predators, disease and dont know how to survive in the wild.
They won't last that long, it would 100% be better to catch them and find a suitable home, or at the very least to feed them and provide shelter.