I was at Sausalito on January 24 during the Herring run and I photographed a third cycle dark gull with a very light iris. At first I thought strongly it was a Slaty-backed Gull and later I was leaning towards Western Gull. I just finished looking at the pictures I took that day and I have now posted six pictures of the bird on my Website and I would like your opinion of which species of Gull this bird is. You can view the pictures at:
Please let me know what you think and if possible, please include what field marks you are using to make your identification so I can learn from this.