Gull ID Needed

I am definitely not a gull expert and as such need the help from those of you who are. The links to these photos were taken on Feb 19, 2005 at Farmington Bay. I was photographing Bald Eagles but when there was a slight lull in the action noticed this little fella. What struck me was that he was so small, the smallest gull around, and there were none others like him that I could see. From the attached photos you can see he has a yellow bill with a solid black tip, and he has pink legs. He is in the 16-17 inch category of gulls as can be seen by the Lesser Scaup that is too his left. He looks a little smaller than the RB Gull that is in the other photo on the left where this gull is on land. He also has black eyes. Behaviors were that he was swimming about (never waded), keeping his distance from the Herring Gulls, not associating with other gulls, searching for food. He went on land in the one photo to get some fish that the eagles had tired of for the moment. He quickly returned to the water. Unfortunately, I did not see him fly and certainly did not want to disturb him to make him fly. I also did not hear him call, though he may have amongst all the noisy Herring Gulls. I had no idea which species he was/is while actually looking at him. I first thought immature RB Gull when I looked at these photos despite the size difference (in one of the photos -7387 seen at the bottom of the photo - there appears to be a winter plumage adult RB Gull in the back ground that is slightly bigger than this gull - and if there were next to each other it seems like the RB would be larger), but neither Sibley's nor Kaufman show a bird like this that I can find. This is not RB immature plumage in my Sibley's. The closest thing I can find, and it is not a match, is the RB immature summer plumage. Just trying to think of all the possibilities. I am wondering about hybrids and perhaps if this produced a ru! nt hybri d that survived. Or maybe even a RB Gull that happens to be molting into his adult plumage, though that would not account for the size difference.

I apologize for not getting to this sooner but I have been a might busy. Also, sorry for the larger size (150-450k) on the photos, but I wanted to give those who can the right opportunity to ID this gull. I have provided several photos. Some give an idea on size, some a better view of the gull. Please either e-mail at birdtalk or at my private e-mail, including why you think whatever it is that you think. I do have more photos but I doubt if they would provide additional help as they are very similar to what you will see here.