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Common Gull L. c. canus, showing wing pattern Photo by Doc Duck Trondheim, Norway, June 2013
Length 40â€“46 cm (15Â¾-18 in), wingspan 100-130 cm, weight 300-550 g [Common Gull L. c. canus; see Subspecies, below, for other subspp.]
A fairly small white-headed gull, with small yellow bill, petite looks, medium-grey mantle, broad white crescents on back, round head, white primary tips show well when standing, and usually dark brown iris. In winter, the head is lightly streaked with dark grey, and the bill often has a narrow dusky to diffuse black band. Juvenile to first summer have white tail with black terminal band; brownish-black primaries; head and body brown to whitish, often heavily streaked; mantle brown in juvenile, grey by first winter.
Ring-billed Gull is slightly larger with slightly lighter back, pale yellow iris, thicker bill with broad solid black ring, narrower white crescents on back, and less white on the primary tips. Juveniles have whiter belly and black primaries.
L. c. heineiSiberian Common Gull. Breeds in Russia and Kazakhstan from around 40Â°E to around 140Â°E longitude; wintering mainly in central Europe, the eastern Mediterranean, Black Sea, and southern Caspian Sea, though a few also west to Britain, and east with L. c. kamtschatschensis to the western Pacific. As L. c. canus, but mantle slightly darker. Population not known, but common in central Europe in winter.
L. c. kamtschatschensisKamchatka Gull. Breeds in north-eastern Siberia; winters western Pacific in Japan, Korea, northeastern China, and far southeastern Russia (Vladivostok area). Length to 45 cm, weight to 600 g. As L. c. heinei, but larger, with a longer, heavier bill and more angular head; legs brighter yellow; iris often light brown in adults; size suggests a transition to Ring-billed Gull rather than Mew Gull. Population not known, but common in Japan in winter.
The above three subspecies are weakly defined, with broad zones of intergradation where they meet.
L. c. brachyrhynchusMew Gull (has also been called Short-billed Gull). Breeds in Alaska and western Canada; winters along west coast of North America from Alaska south to Baja California, rare elsewhere in North America (but recorded east to Atlantic coast). Length 38-41 cm, wingspan 100-120 cm, weight 325-495 g. Adult plumage similar to L. c. canus but with less black on wingtips, head more heavily streaked and bill with less black smudging in winter; iris mid brown, sometimes yellowish. Structure differs more, with relatively longer wings and more rounded head; bill shorter and weaker, and with less black marking in winter. Juvenile plumage markedly different, with uniform dusky brown head and underside, much broader blackish-brown tail band (no white base), and browner wings. A scarce taxon, with a population of little over 10,000 pairs.
Common Gull L. c. canus, juvenile Photo by Bobby65 Leksand, Sweden; August 2005
The once-split subspecies L. c. brachyrhynchus has now again been lumped with Larus canus. The common name Mew Gull is recommended by all the major taxonomic authorities for the merged species, despite this not being the name of the nominate subspecies, and being far less widespread and abundant than Common Gull. The species continues to be known as Common Gull in Europe and Asia. The only world-wide authority to recognise the split of Mew Gull from Common Gull was the 1996 installment of Sibley and Monroe, though they are also treated as separate species in Olsen & Larsson's monograph (2003) and in a major study by Adriaens & Gibbins (2016), a trend likely to increase further in the future.
Natural habitat by lakes and marshes in the breeding season and along coasts in winter; within last century or so has become strongly adapted to human commensalism, feeding on ploughed fields, meadows, and sports grounds, or in streets on human-supplied food, and using roofs in urban areas (particularly industrial estates) to nest and rest. Outside of the breeding season, often flies often long distances (up to 20-30 km) every evening to roost at sea or on large lakes and reservoirs.