American Wigeon x Mallard Hybrid ~ Karuizawa

Ok so now it turns out this is the first record ever of this hybrid combination in Japan.

I am sorry, but that is just a not fully moulted mallard.

No Wigeon x Mallard Hybrid shows the mallard tail locks , independently which wigeon species is involved.
See here American wigeon x Mallard hybrids:
American Wigeon x Mallard (hybrid) - Mareca americana x Anas platyrhynchos - Media Search - Macaulay Library and eBird