Tundra Swan - Cygnus columbianus

Last weekend we joined Terry Colborn and friends on a trip to refuges in the Central Valley (north on route I-5). One of the highlights of trip were the many flocks of Tundra Swans, seen overhead and foraging in flooded rice fields. Impressive groups were seen west of Williams, and east of Willows off of SR 162 (roads Y, Z).

The Tundra Swans are wary, always foraging a bit away from the roadways, so viewing is best with a scope. The flocks of 50-100 birds travel and forage together, made up of family groups. The adults mate for life, and the young of the year accompany the parents to the wintering grounds. Here we see a pair of adults swimming with a hatch year youngster with its gray neck. The yellow staining of these birds, especially on the neck, is probably caused by iron in the water.

As we watched the larger group it was apparent, even at a distance, that some of the adults had a variable amount of yellow at the base of the bill, in the area in front of the eyes known as the "lores". Some thought they saw one swan with a lot of yellow, indicating it might be a Bewick's Swan. I don't think I saw that individual, so I focused on this family group which did show a good bit of yellow. Distance was about 250', so detail is lacking. Note the gray neck on the young swan in the second photo, and the variation of the yellow on the bill in the adults. A closer view of the adults shows the yellow better:

Easy to get your mind around the world's swans, as there are only about 7 or 8 species. In California we see mainly the Tundra Swan and the increasingly common introduced species, the Mute Swan, with a occasional appearance of Trumpeter Swans, and the very rare sighting of the Whooper Swans.

So what is a Bewick's Swan? In the past authorities such as P. Johnsgard (Ducks, Geese and Swans of the World) recognized Bewick's Swan as a distinct species, Cygnus bewickii, distinguished by the large amount of yellow on the bill. Most authorities now consider the Bewick's Swan to be a subspecies of the Tundra Swan, i.e. Cygnus columbianus  bewickii. The nominate Tundra Swan, C. c. columbianus is sometime referred to by its older common name of Whistling Swan. To further complicate matters it appears that intergrades of the 2 subspecies are known to exist, i.e Whistling Swan x Bewick's Swan.

I guess the lesson for me was that the amount of yellow on the bill of the Tundra Swan is quite variable, so caution should be observed in calling any given individual a Bewick's Swan. Not that it matters to most of us who just enjoy watching these awesome swans and listening to their musical honking as they fly.