Maybe....I don't know how to describe the sound. That's interesting - I would say it's definitely some sort of male display. I've searched online but haven't seen anything about it!
I have two male runner ducks who are 3 months old. I've noticed that when they're swimming in the pond and they might be excited by the other ducks they will do something odd - kind of push themselves up, then put their heads down towards their chests and make a really strange noise - I hesitate...