Confusing female wigeon

A confusing female Wigeon was in flock of Eurasian Wigeon at Mukawa (left one).
It is seemed to be a female American wigeon.
The feature of American is grayish head and white wind flap. But I didn't see its wind flap...
A male American Wigeon stayed here one month ago. This female was looked paired with Eurasian Wigeon (right one). Is it Hybrid?

Right one is Eurasian and left one is pending individual.



Common Scoter.

Mukawa, Hokkaido. 14th/Apr/2012.