Common Gull (Larus canus canus)—Ringer—and Short-billed Gull (Larus brachyrhynchus) together at Sandy Beach, Cohasset, MA; April 15, 2018. Photograph by Marshall J. Iliff. https://macaulaylibrary.org/asset/94808371

Mew Gull (Larus canus) has been known as a vagrant to Massachusetts ever since the first specimen was collected in Chatham in 1908. By 1857, its four distinct populations had been described, but reliable field marks for identification to subspecies level remained extremely poorly known until the 1980s. Veit and Petersen (1993) categorized the records of Mew Gulls in Massachusetts by subspecies—L. c. canus and L c. brachyrhynchus—and by distinct seasonal patterns. Only in the past decade or two, with advances in digital photography, have North American birders been fully equipped to identify and document the various taxa in the Mew Gull complex. In the process, a more complicated and interesting picture has taken shape in Massachusetts and along the Northeast coast.