From what I have heard and seen, sometimes they can get over a low fence, or coast downhill a bit, or do some wing-assisted jumping.
But as far as I know, those breeds, especially mature birds, would not be likely to take off and fly more than a few yards at most. Not like wild mallards or muscovies.
I'd thought they couldn't, and then mine got lift. Since Pepper and Salt are drakes, I really don't want them getting out. They are twice the size of Bert (mallard drake) and they've been having stand-offs through the fence with him.