Hybrid wigeon
As one of the SPEC volunteers pointed out to me, this dude is an American / Eurasian Wigeon hybrid. His body has pretty much Eurasian Wigeon colours, while his head has the green side patches of an American Wigeon, with the rest being Eurasian-red.
The two species have different stomping grounds but are otherwise extremely similar in habits and habitats. The few Eurasian Wigeons that find their way here will happily hang out with their American relatives for the season, and sometimes make babies with them.