Pretty flock, don't know the ID either. The background seems very noisy from here, good thing they are not merging with each other except on the first two.It would make a great pano, once ethe noise is removed.
Judging by the amount of white on the wings, I'd say you have a nice flock of Greater Scaup ducks. I think a pano crop would improve this & some NR on the background would help.