I introduced ducklings to 2 existing dogs - a greyhound and a doberman last August
I let the ducklings settle in before introducing the dogs to them. I held them and showed them they were mine and not for them to eat or play with. When I moved them from their kennel to the bathroom to play on the floor, I'd show them to the dogs if the dogs were around. If the dogs stuck their nose in the kennel, somebody usually ran over and nipped them on the nose. Didn't take many times before they decided they weren't all that interesting since any time they peeked in, they got bit by a duckling.
Now Jet (greyhound) knows they lay eggs and will check where they are to see if they left her anything. I think she'd pick them up and look under them if she could
Ally flew off the deck one day and landed on Jet and it didn't bother her, she jumped and looked at me and walked off. Another day another one of them landed on Tavarish (doberman) and he didn't care either.
Jet is aware of where they are and doesn't intend to bother them, but they usually run off when they feel she's too close.
Tavarish ignores them to the point he has no clue where they are and often about plows them over when he is out running in the yard - they get out of his way.
I'm now introducing a new dog (14 month old great dane) to the ducks. So much easier introducing ducklings to a dog than a new dog to existing ducks. She seems to think they are play things. The ducks are not amused. Today is a week and the ducks are more trusting of her and she's being pretty good about ignoring them. Though today she decided to walk over and see if should could sniff them. They didn't like that and quacked and took off. I told her no and squirted her. But they aren't getting up to run away when she's 6 feet or so away, so things are going well. I'm not about to let her out without me out there keeping an eye on her and the ducks, but I think we'll get there with some more work and vigilance.
Helps that my girls think they can take on moose! Three and a half pound blue ducked her head down and chased 80+ pound Abby the dane off the other day.
Some pics of dog/duckling introductions through the first month or so.