Last year when I visited the eider ducks there were just females nesting, and they do quack a little bit. Earlier in the season male ducks are around, which look rather different and also sound very different. I think they are softly cooing to gain a mate, but I have no idea really. Have a listen for yourself! The eider ducks like hanging out between two dog enclosures, safety from foxes, so there might be an occasional howl as well.
I heard a less peaceful noise for the first time last night too, the angry shrieks of the arctic tern. I'll try and capture that when they are more prolific. I can't say I'm looking forward to their dive-bombing antics, hopefully they won't decide to nest too near my door!