x2 what jdywntr said. Slow and steady movement, work in pairs, and herding is what works best here. Usually after 305 days of a new routine the ducks figure out whats up and work with us at bed time.
owl, skunk, raccoon, weasel, dog, coyote, fox, you name it anything can and will grab a free meal of domestic duck. Sorry you suffered a loss, but as Lydia mentioned you need to provide them secure night time housing to protect from predators (geese arent guard animals and wont protect...