Tufted Duck x Scaup hybrid?

No rain today but still pretty gloomy. I gave Østensjøvannet a go and was able to note that numbers of birds are only falling slowly so there is clearly enough food still available despite the onward march of winter. There was nothing of any particular interest to see although I thought I had a Scaup (bergand) which would be a good Oslo bird. It did not feel 100% right though and zooming in on the pictures I took shows that the black nail on the bill looks to be too large for Scaup (or is it?- some people think its OK for Scaup)  but matches Tufted Duck (toppand). I am struggling though to see this bird as a pure Tufted Duck though and reckon it may be a hybrid between Scaup and Tufted Duck although it is rather difficult to ever prove such a hypothesis. 

A Tufted Duck or a hybrid with a Scaup or a Scaup? Head profile and the pale patch on the cheek are strong Scaup features. The white around the bill is also a Scaup feature but can be shown by Tufted Ducks. The large black nail on the bill though looks to be too extensive for a Scaup and matches Tufted Duck.

some of the other waterfowl today