Dark-billed immature, 18 January.
Immatures still lighter-billed, 2 December.
Tundra Swan C.c.columbianus also occurs in the region in small numbers and can be found at Lake Biwa or elsewhere but I don't find birds every year even though it might be expected that birds would return to the same location in successive winters, particularly where family groups are concerned.
Not all birds are as obviously columbianus, the following shots are of a family party at Kokoku, Biwako. The first bird would be a good contender in its own right but the second has quite extensive yellow on the bill. The immature has very limited pale areas on the bill and again looks good. Collectively they are quite convincing.
I've never encountered Whooper Swan at Lake Biwa and their appearance in the region seems unpredictable but it's possible to bump into singles mixed in with flocks of Tundra Swan.
Whooper Swan in southern Hokkaido.
Trumpeter Swan is a rarity in Japan and those that do occur would be expected in the north, so a bird at Lake Shinji (Shinjiko), Shimane prefecture came as a huge surprise and was really popular with birders, particularly as other birds at this location during the winter included Ruddy Shelduck, Pied Avocet, Common and Arctic redpolls and Snow Bunting.