My first 3 geese (chinese) were raised by the seller with ducks. So I put them with my ducks and had no problem. Then in the spring I gave them baby ducklings to raise. They loved them!
Then in late summer, I traded two of mine (adults) for two (juveniles) a friend had. That left one of my adult geese to show the two new ones the ropes.
They seemed to get along with the ducks very well, until recently. Now I think the new gander is trying to mate the young ducks. It will look like he is biting her neck and trying to wrestle her to the ground. She quacks and tries to get loose. After a while (I watched to see how they would handle it) he stopped, she shook herself off and walked a few feet away, and that was it.
That led me to believe that he wasn’t trying to kill her, or else they would not have stayed near each other. Now, with the size difference, I’m sure he could do some damage, trying to mate a duck. It is my hope that when he realizes he has two geese to mate with, he will leave the ducks alone. I hope he hasn’t permanently bonded with the duck. Then I would have to separate them.
Edit to add: Now that I think about it, since the duck was raised by geese, she might be bonded to the gander. She might actually be willing to mate with him. I’ll have to rethink how I’m handling this.