I would never leave the dogs unattended with your ducklings, for sure. Ducklings are so fragile, they could even kill them accidentally.
Some dogs will never be trustworthy around birds. Their prey drive is too strong. You just can't break instinct. We have a mutt who constantly lunges and barks at the ducks. I've trained her to have some self-control, but again, you can't break instinct. When she sees them, it's like her mind goes blank and she isn't capable of understanding a command or discipline or anything. She can't think of anything but catching the ducks.
But we just got a GSD puppy, Nora, last week. I'm hoping she will be trustworthy around our ducks, with some training. I want her to learn she can "look at but not touch." She seems promising so far. Kiwi our broody duck has been quite helpful. She was fine with Nora coming relatively close, but when Nora tried touching Kiwi, she got a nip on the nose. She backed up, tried it again, got the same response, and stayed back. Kiwi's a great dog trainer!
If your dogs know the phrase "don't touch," or "easy" anything similar, I think they're the best phrases when introducing something like that to your dogs. You could show them the ducklings, on-leash of course, warn them not to touch them, praise them if they're behaving well, gently correct them and pull them back if they get too rowdy, etc. I would introduce each dog to the ducklings individually, because you just can't control five dogs at once.
If they don't know "don't touch," by the way, it's a very useful phrase to know! Just recently I had to put some eggs down within my dog's reach, temporarily. I just told her, "don't touch" and she looked at them hopefully, but stayed back.
Fortunately, the one time I had to use one, when a mother abandoned her ducklings, it was warm and I only needed it during the night, and only for one week.
