Ring-billed Gull delawarensis 1st cycle, December 30 2012, Louisiana (Ronnie Maum). Pink base of bill. Plain grey on greater coverts. Proximal half of tail also with lining and spotting.

Ring-billed Gull delawarensis 1st cycle, December 30 2012, Louisiana (Ronnie Maum). Dense chevrons on flanks and side of breast. Chequered pattern on greater coverts. Proximal half of tail also with lining and spotting.

Common Gull canus 1st cycle, January 02 2011, Warmond, The Netherlands (Maarten van Kleinwee). Most of the scapulars replaced. Few dark markings on upper tail coverts, and tail with broad dark band.

Common Gull canus 1st cycle, January 29 2011, Leiderdorp, The Netherlands (Maarten van Kleinwee). Scapulars replaced, all wing feathers (coverts, tertials, secondaries and primaries) are first-generation, brown feathers. Especially the median and greater coverts look bleached.

Common Gull canus SVS 7187947 10+CY, January 262013, Pas-de-Calais, France (Jean-Michel Sauvage). Classic Common Gull in winter, note very dark iris, obvious band on bill, bill colour rather greenish yellow, not vivid, same for leg colour, very delicate 'pencil streaking' on head, concentrated on crown and not in hindneck or running down to sides of breast, much white in wingtip with very large mirror on P10 visible.

Mew Gull brachyrhynchus adult, September 25 2006, Ship River, Anchorage, Alaska. (Greg Forcey). Mottled dark pattern on head, concentrated in hind neck, and continuing on breast. Small tips on outermost primaries and full broad sub-terminal band on P10. Yellow legs, yellow bill without black band, pale honey iris.

Common Gull canus NOS 5138897 18CY, November 26 2013, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Classic Common Gull in winter, note very dark iris, band on bill, bill colour rather greenish yellow, not vivid, same for leg colour, very delicate 'pencil streaking' on head, concentrated on crown and not in hindneck or running down to sides of breast, much white in wingtip with very large mirror on P10 completely merged with white tip. Also large mirror on P9. No black on P5.

Mew Gull brachyrhynchus adult, February 26 2006, California, US. (Glen Tepke). Mottled dark pattern on head, concentrated in hind neck, and in this bird only slightly continuing on side of breast. Small tips on outermost primaries. Yellow legs, yellow bill without black band, pale iris.

Common Gull canus DEH IA052611 12CY, February 02 2013, Calais, France (Jean-Michel Sauvage). Very dark iris, band on bill, bill colour rather greenish yellow, not vivid, same for leg colour, very delicate 'pencil streaking' on head, concentrated on crown and not in hindneck or running down to sides of breast, much white in wingtip with very large mirror on P10 and large mirror on P9.

Mew Gull brachyrhynchus adult, January 16 2007, Broughton Beach, OR. (John Rakestraw). Mottled dark pattern on head, concentrated in hind neck, and continuing on breast. Small tips on outermost primaries and full broad sub-terminal band on P10. Yellow legs, yellow bill without black band, amber iris.

Common Gull canus EN58 adult, June 17 2010, Zoetermeer, The Netherlands (Maarten van Kleinwee). Dark iris, short tongues on outer primaries hardly visible on P8 from above. Black on P5 worn away. Black on P6 runs back upwards along outer edge of feather. No string of pearls (white tipped tongues).

Mew Gull brachyrhynchus adult, January 27 2010, Mercer Island, Washington (Dennis Cheasebro). Mottled dark pattern on head, concentrated in hind neck, and continuing on breast. Small tips on outermost primaries and full broad sub-terminal band on P10. Yellow legs, yellow bill without black band, amber iris. Slightly heavier billed bird, probably male.

Common Gull canus adult, January 02 2011, Warmond, The Netherlands (Maarten van Kleinwee). Mirrors on P9 and P10 (on both the inner and outer web). Short pale tongue on P8. Black on P6 running up along outer edge. Dark iris and bill band, neat fine streaking on head, not on breast.

Mew Gull brachyrhynchus adult, January 03 2012, Sayer's Park, Lake Washington (Amar Ayyash). Note very deep tongue on P8, and tongue >50% of length on P9. Black on P6 not running upwards along outer edge as in canus.

Common Gull canus adult, November 10 2012, Esbjerg, Denmark (Graham Ekins). Small mirror on P8 (not uncommon in canus). Short pale tongue on P8. Black on P6 running up along outer edge. Dark iris and bill band, neat fine streaking on head, not on breast.

Mew Gull brachyrhynchus adult, October 10 2008, Richmond, BC. (Punk Birder). White tongue tips (string of pearls) with sharp division between grey and white, black on P6 not running upwards along outer edge as in canus, deep tongue on P8.

Common Gull canus, adult, January 17 2013, Blennerville, Ireland (Vivian Wynne Philips). Dark iris, band on bill, short tongues on outer primaries.

Mew Gull brachyrhynchus adult, January 03 2012, Sayer's Park, Lake Washington (Amar Ayyash). Note white tongue tips (string of pearls) with sharp division between grey and white; black on P6 not running back upwards along outer edge as in canus; dense boa in the neck; large tips on secondaries and inner primaries.

Mew Gull brachyrhynchus 1st cycle, September 28 2012, SSM Landfill, US. (Kirk Zufelt). Blackish tail, dense barring on uppertail coverts. Juvenile plumage.

Common Gull canus 1st cycle, December 07 2012, Leiden, The Netherlands (Maarten van Kleinwee). Narrow black tail band, white on uppertail coverts and rump.

Mew Gull brachyrhynchus 1st cycle, January 15 2011, Off San Luis Obispo County (Brad Schram). Blackish tail, texture connects hindneck with breast and belly, dense barring on uppertail coverts.

Common Gull canus 1st cycle, January 25 2009, Cascais, Carcavelos, Portugal. Picture: António A Gonçalves. Some 1st cycle Common Gulls get blotchy in the hindneck, but still there remains a spotting pattern, more obvious on the crown and ear coverts. Note much white in the tail.

Mew Gull brachyrhynchus 1st cycle, October 31 2011, Virginia Lake. (Kirk Zufelt). Very mottled texture connects hindneck with breast and belly. Broad bands on undertail coverts.

Common Gull canus 1st cycle, January 02 2011, Leiden, The Netherlands (Maarten van Kleinwee). Breast-pattern of first-cycle Common Gulls is quite variable: from pure white, dark-patterned flanks, to fully-dark breast and flanks as shown in this individual. However, dark hindneck not solid, no shawl, but striped and spotted.

Mew Gull brachyrhynchus 1st cycle, February 02 2011, Washington (Dennis Cheasebro). Blackish tail, texture connects hindneck with breast and belly, overall simple pattern (actually no pattern) on coverts. Note worn plumage.

Common Gull canus 2nd cycle, November 10 2012, Esbjerg, Denmark (Graham Ekins). Bill and and dark iris. 2nd winter canus may have head streaking more mottled and blotchy. Lacks black ink spots on tertials and tail.

Mew Gull brachyrhynchus 2nd cycle, February 21 2009, Dana Point, Orange Co. (John  Avise). Mottled dark pattern concentrated in hind neck, and slightly continuing on side of breast. No tips on outermost primaries. Ink spots in tail on tertial centra.

Mew Gull brachyrhynchus 2nd cycle, February 04 2011, Richmond, BC. (Punkbirder). Ink spots on tertials.

Common Gull heinei 2nd cycle, January 2010, Copenhagen, Denmark (Kjeld Tommy Pedersen). Measurements indicate heinei. Heinei more often tend to show immature markings to a large extent in 2nd winter. Note elongated head and compare to rounded head and fine bill of Mew Gull.

Mew Gull brachyrhynchus 2nd cycle, January 03 2012, Sayer's Park, WA. (Amar Ayyash). Ink spots on tail, broad white tips on secondaries.

Common Gull kamtschatschensis 1st cycle, January 25 2012, Jinzhou Bay, China (Terry Townsend). Dark brown, well marked upperparts and barred uppertail coverts. Moult seems to be later than in ssp heinei.

Common Gull kamtschatschensis 1st cycle, January 25 2012, Jinzhou Bay, China (Terry Townsend). Dark, well marked underparts and strongly barred undertail coverts. Large stocky bird with stronger bill than Common Gull canus.

Common Gull heinei 1st cycle, January 25 2012, Jinzhou Bay, China (Terry Townsend). Cleaner than kamtschatschensis, especially the uppertail immaculate white, and more advanced moult on the scapulars.

Common Gull kamtschatschensis? 2nd cycle, January 28 2012, Zhuanghe, China (Terry Townsend). Either kamtschatschensis or heinei. Large stocky bird with stronger bill than Common Gull canus. Moult seems to appear somewhat retarded compared to ssp heinei: still black markings in tail and on several secondary centres. Extensively brown in greater primary coverts. Many coverts have brownish fringes, which may proof to be a good feature of second winter kamtschatschensis.

Common Gull heinei adult, December 29 2012, Aktau, Kazakhstan (Kadirov Aisagali). Deep black full subterminal band on P5; black pigmentation extends all the way to the primary coverts on P8, extensive black on P7, in this bird there is a slight bayanoet on P7, not on P6.

Common Gull heinei adult, January 2010, Copenhagen, Denmark (Kjeld Tommy Pedersen). Measurements indicate heinei.

Common Gull kamtschatschensis adult, March 13 2010, Choshi, Japan (Goodhilda). Largest of the Common Gull subspecies, strong bird with attenuated rear end (P5 longer than tertial #3).

Common Gull kamtschatschensis adult, February 21 2010, Choshi, Japan (Goodhilda). Sloped forehead and longer bill may suggest Herring Gull at first glance, but Common Gull never develop a red gonys spot.

Common Gull kamtschatschensis adult, March 13 2010, Choshi, Japan (Goodhilda). No black band on the bill. Note deep pale tongue on P8 (about 75%); and tongue on P9 about 50% of feather length, measured from coverts.