Okay, it seems I have some explaining to do. I my last post, I thought I had found a Thayer's Gull. Several things about the bird didn't seem quite right to me, and I thought it might even be a Glaucous-winged Gull, which is much rarer in Utah (although Thayer's are also pretty rare here). So, I sent photos and videos to several list-serves requesting help in my identification. I received responses from nine different people, and as any student of the gulls would guess, there was little consensus. Opinions ranged from pure Thayer's Gull to pure Glaucous-winged Gull to pure Slaty-backed Gull, but the most common opinion was that I had photographed a hybrid between a Glaucous-winged Gull and a Herring Gull. This was one of the possibilities I had considered, but it wasn't the identification I thought was most likely. Even after hearing all the opinions of the experts, I am still not confident in identifying this bird, and it will stay in my records as "Unidentified gull, probable Glaucous-winged x Herring hybrid".
Someone asked me before if it's embarrassing to publicly misidentify a bird. If I had called this something outlandish, then maybe I would be embarrassed. But gulls are notoriously difficult, and I feel pretty good about how I did with this one. In fact, David Sibley says of the Thayer's Gull, "Very difficult to distinguish from hybrids of other large gulls such as Herring x Glaucous-winged." After all, if the gulls can't even tell each other apart when it's time to find a mate, how can we be expected to sort them out as juveniles!
Okay, so I'm not counting the Thayer's Gull that I posted about before. Then why is Thayer's Gull still in my year list at the right? Well, I feel more confident in the identification of a different bird that we saw on the same day was a Thayer's Gull. One photo of this bird is above: the Thayer's is on the left and a California Gull is on the right. This Thayer's Gull has darker wingtips than my previous mystery gull, but it has a distinctly small, round head and petite bill, two traits I was looking for on the mystery gull but was having trouble with. So, the photo may be wrong, but I still think I saw a Thayer's Gull that day. Although I'd be happy to hear comments from the experts about this gull as well.