Ok, so ducks don't mate for life then? I guess once my one drake lost his mate last week, to the owl, he must be breeding the only female left then?One too many drakes mating a female. I'd separate the female give her a break. If you introduce the ducklings to her you'll have to di it slowly for one thing 3-4 weeks old ducklings aren't almost grown and can be injured by an adult duck so introduce through fencing so they can meet but not touch. And before introiducting to your drakes they need to be breeding age if you have any females or the drakes can injure them. This whole process is going to take a bit of time.
Drakes are rough on females if one particular drake is being over the top then maybe it's time to rehome.