Yes, a lot of domestic Aylesbury ducks do escape if their wings are not clipped and some are just put into rivers by people fed up keeping them. Aylesbury are the ones most often sold for eating. We kept a large variety of ducks including rare breeds, they will live together quite well. We also never clipped their wings, but they all stayed.
If they are fed, it best to feed with wholemeal bread as white bread makes them ill. They also love lettuce.