My ducks still attack the geese during breeding season. We keep them separated except for the coldest part of winter when they are all happy to snuggle. We can't let them all out together from early spring until early fall because the drakes will relentlessly try to mount the geese - male & female geese. My geese have never had any success with their broods and I wonder if the stress the ducks bring has had an effect on them. In fact, when its time to break up the nest, I always break the eggs and there has never been a fertile one.