The swan seen recently (possibly still there) at the Andree Clark Bird Refuge sparked quite a bit of discussion. I brought the bird up on ID Frontiers to get international input, and whilst the number of responses was underwhelming, there seems to be consensus that the bird is not a Tundra Swan, at least not 100% Tundra. Most feel the bird is a hybrid, with one of the parents being Mute Swan. The other parent is more of a mystery. It is felt there is too much yellow coming in on the bill for it to be of Tundra origin. That leaves us with Bewick's and Whooper, both European species, with most votes going for the latter.
So from whence did this bird arrive? It seems most likely it's an escape from a collection. The birds relative tameness would point to such a conclusion.
This is, of course, all conjecture. As Louis Bevier wrote, "Get some poop or feathers. DNA is the only way!" And as I said to him, "I'm not wading into the Bird Refuge."
On a different note, I was at Lake Los Carneros this afternoon and heard what was a dead ringer for Kentucky Warbler singing across the lake from the dam. I've been fooled before, and at the same location, to boot. Common Yellowthroats can occasionally give songs that are extremely similar to Kentucky Warbler. I did, however, walk around to check it out; and of course the bird had shut up by the time I got over there. If this were mid-May or June the chances of Kentucky Warbler at LLC would be greater than on April 20th.