I finally got over my Costa Rica birding hangover today and went out, which turned out to be a good idea, because it resulted in my first California Slaty-backed Gull...a state nemesis bird, now defeated. It was in the gull swarm at Sausalito, which has congregated to feast on herring eggs.
Here is a typical Western Gull for comparison. Note the clean head, yellow-orange bill and dark, beady eye.
No, the Slaty-back is not in the act of hybridizing in this photo.
The most reliable way to identify Slaty-backed is by call.
Ok thats not true. It's all about the string of pearls! Stoked.