30 April 2019
Age: Our quiz bird is the dark-backed gull right of center. This appears to be a relatively large, 1st/2nd cycle type gull. The broad white tips to the tertials, extensive non-juvenile upperwing coverts, lack of any mirrors on the outer primaries, and the considerable amount of white on the uppertail seems to suggest a 2nd cycle. The outer primaries appear to have pointed tips and are indeed 1st basic (juvenile) flight feathers. However, the start of the 2nd prebasic molt is signaled by the inner primaries being in active molt (difficult to see here, although p5 has been dropped).
Identification: Noticeably larger than the surrounding Ring-billeds, but not much so. This dark-backed gull has a relatively straight, tubular, bill with little expansion to the gonys. Looking closely, the eye is beginning to pale. The fine streaking above the eye, on the crown and hindneck, as well as the dark upperparts, make Lesser Black-backed Gull the best choice.
Sheboygan, Wisconsin. June.