I'm not convinced it is dominance, either. I actually wanted it to be an expression of affection, but others convinced me it was dominance related. Do you think the mother duck could be establishing that she is the boss over her ducklings? Just an idea, I'm open to other ideas.I dont know if it is necessarily only a dominance thing I see a mother duck at my local park do it every time she has had ducklings. She kind of does the vibratey neck thing and then just jently preens or nudges them. I don't really think there is anything you should do as long as she stays gentle
Usually I'm pretty clear on my duck communication, not so much on this one. It hasn't happened often enough, I think.