Regarding the yellow-billed swan seen first south of Snohomish, and recently south of Conway, presumably the same bird, I would recommend a look at Keith Brady's pictures taken from Elliot Road, near Snohomish, on Dec. 26th. They are at:

http://www.pbase.com/slickslug/washington_rarities<http://www.pbase.com/slickslug/washington_rarities>

Both pictures show the yellow consuming more than half of the (upper) bill, with a wedge shape appearing to extend under the nostril. This looks most evident in the second of the two pictures.

In the reference, Birds of Europe, a Princeton Field Guide, it states that distinguishing between whooper and Bewick's can be difficult, when observing single birds. "Safest separation by pattern of bill, Bewick's having slightly less yellow than black, the yellow generally a square or rounded patch (diagnostic)..." But then it goes on to say the yellow can be rarely wedge-shaped, but yellow not reaching in front of nostril. This guide considers Bewick's to be a subspecies of the tundra swan.

The illustrations in the Birds of Europe guide would incline me to put the bird in the Brady photos into the whooper category, notwithstanding a whooper's prior presence in this area as unknown or unrecorded. I must acknowledge that others more expert than I should weigh in, as I've certainly never seen either bird in the wild before. Of all the photos of a Bewick's that I saw on Google sites, none had a wedge-shaped yellow patch extending more than half way down the bill.

Bill Boyington
Shoreline, WA
wrboyington at msn.com<mailto:wrboyington at msn.com>