I observed Ferruginous Dock × Pochard first time last month. This female looked so cute. Reddish-tone was weak than female Ferruginous Dock. This pattern tip of bill is typical of hybrid according to An identification guide to the duck of Japan. When I saw this individual, I though it was young. But after I heard that this individual returned to Niigata and had observed last year.
Stand out in the flock because of the strong reddish-tone. I never seen not-hybrid Ferruginous Dock but I think the figure of body is similar to Ferruginous. Flank was similar to Pochard and the color of upperparts was intermediate between two species. There were no special behavior. Suffice it to say is that they were a little shy. Branch of Galloanseres (Ducks & Landfowl) was 90 million years ago. But the radiation of ducks was relatively recently so there are many cases of Hybrid. Anyway, It is interesting that there are unique Hybrid examples like Mallard × Merganser.