Yesterday morning, before we left Massachusetts, we spent a few more hours birding around Gloucester to get better looks at some of the birds we had seen during the Superbowl of Birding on Saturday. (I will have more to say about the competition in a future post.) At our first stop, in Gloucester Harbor, there was an interesting gull near the pier where many gulls normally roost. on top of a green warehouse. Most of the more knowledgeable birders present believed it to be a 3rd winter Slaty-backed Gull, a rare species along the eastern coast of North America, but one that has appeared around Gloucester before. If you have not already done so, take a look at Corey's post, which has photographs of the gull in question and summarizes points in favor of the bird being a Slaty-backed Gull. If you have an thoughts on the identification, especially if you know a lot about gulls, please leave a comment there.