White-winged Scoter

The White-winged Scoter is a large American diving duck. The old taxon Brown Scoter has recently been split into 3 new species, the Eurasian Brown Scoter (or simply Brown Scoter), the Siberian Scoter that occurs in the east of the continent and the White-winged Scoter which nests in the north of the North American continent. The White-winged Scoter has thus become monotypic. This is what I'm going to treat here. The White-winged Scoter is very close in all respects to the Brown Scoter, to the point that the taxon is not yet recognized by all. It is recognized by the IOC*, which is why it is taken into account by oiseaux.net. I will only speak of what differentiates it from the brown.
It is the bill of the adult male that must be looked at properly. It is quadricolored, black, yellow, orange and pink. The black basal bulb already exists more developed than that of the male brown. The upper mandible, black at the base, is yellow in its upper part and pink on the sides, bordered by a black commissural line that widens forward. The nape is orange. The lower line of the bill, seen in profile, is straight while it is convex in the brown. Furthermore, the forehead is more rounded.
The adult female is dark brown, often with lighter spots more or less developed on the sides of the head as in the brown. Some have practically none. The bill is black to dark grey, without basal swelling, sometimes with reddish tones on the sides and towards the nape.
The juvenile is paler in plumage than the adult female, with more distinct pale spots on the sides of the head. Immature males in their 2nd year can be problematic and resemble females, but in principle, their plumage is darker.