Big news! The Mew Gulls have been split into two species, Larus canus and Larus brachyrhynchus. The proposal, put forth by Pamela C. Rasmussen back in November of 2020, can be found here. Data that bolstered the split comes from a combination of genetic, morphological and vocal differences, in addition to well-established geographic isolation of brachyrhynchus.
In the 62nd Supplement to the AOS Check-list of North American Birds, Short-billed Gull is the name "resurrected" for the American taxon, Larus brachyrhynchus (formerly known as Mew Gull to North American observers).
The canus group now includes Old World taxa, Common Gull (nominate L.c. canus) and Kamchatka Gull (L.c. kamtschatschensis). Nominate is rare to Newfoundland, Nova Scotia and Quebec, and casual south of here to NY. Beside being very rare in Alaska, Kamchatka is casual, but increasing, in the Northeast from Atlantic Canada, down to New England. The supplement makes no mention of the less known race, heinei, or Russian Common Gull (L.c heinei), as it is known in Europe and Asia. There are no known reports of heinei in North America, possibly due to an observer bias. Field identification of all four forms -- with helpful notes on vocalizations -- can be found in Adriaens & Gibbins (2016).
The addition of Short-billed Gull puts the number of gull species on the ABA Checklist at 31.
|1st cycle Short-billed Gull (Larus brachyrhynchus) with adult California Gull.|
Washington. January. photo: Amar Ayyash.
|1st cycle Common Gull (Larus c. canus) with 1st cycle Ring-billed Gull.|
New York. December. photo: Andrew Baksh.
|1st cycle Kamchatka Gull (Larus c. kamtschatschensis) with adult Vega Gull.|
Japan. December. photo: Amar Ayyash