What makes you think they are Scaup, Hendrix?!
Scaup has no head crest as far as I know.
I believe your images show they are female Tufted Ducks. See the short crest there ... : Author: Hendrix Time: 10/02/2007 23:53
the white band around bill of female Tufted is smaller ?
Ialso see 3 of them in a group of Tufted , only tell by short crest or not ? Author: ajohn Time: 12/02/2007 14:06
This is a female tufted duck.
I find female tufted are very variable and can be confusing, often looking a bit like scaup. The white band around the bill is a fairly common feature in tufted and is not exclusive to scaup, not an exclusive identifying feature. It is typically larger and rounder on scaup.
Female scaup would look bigger, rounder-headed (no crest), broader and longer-bodied and heavier-billed. Also the bill is mostly grey with very little black on the tip (not in a broad band around the tip as in these photos)
There was recently a very good photo posted on the forum of a pair of scaup in flight to compare with this bird. Author: Hendrix Time: 14/02/2007 20:55