i have australian spotted ducks and i would love to get some runners too. but i don't want them to have to be penned up. our property is 1.5 acres and all fenced in so the aussies have free run of the land. so will they breed even though they are different sizes? i would like to hatch the runners myself, but if they will crossbreed i suppose i could just order sexed ducklings from a hatchery....