I have kept several kinds of ducks over the years and found that the only ones that fly are the small kinds (mallard, call ducks, mandarines, etc.) and of course muscovies (only the females though, the males are too heavy). My Indian runners and Campbells did not fly, not even when chased, but, oh, can they run! Geese can fly, but generally do not bother. I know of a farmer who has a small flock of geese, that flew down to pasture every day, but came back when called. I hear that geese may fly away when wild geese pass overhead, but have not heard the same of ducks. I do know of people who have lost mallards, woodducks and mandarines, but mostly when they were frightened. For that reason I always cut the feathers of one wing of my smaller ducks, female muscovies and egyptian geese, but had some narrow escapes when careless after the mold. It is best to only cut one wing, to throw them off balance, because they can still fly if both wings are cut, although with much more difficulty.