Ring-billed Gull Larus delawarensis
1, presumably second winter, Suncheon Bay, Jeollanam Province, May 3rd 1997.
Although the structure, mantle colour and bare parts colour clearly match Ring-billed Gull and should rule out Kamchatka Gull, the kamtschatschensis subspecies of Mew Gull Larus canus, several minor features seem to make ageing of this individual problematical.
An obviously pale-mantled Common Gull-type, in with four obvious kamtschatschensis Mew Gulls, was found on the tidal-flat at Suncheon Bay on May 3rd 1997. It was watched for about 3-5 minutes from an anchored boat in shallow water, through 8x40 Nikon binoculars and for about 1 minute through a tripod-mounted Nikon telescope (20-45x zoom lens), at between around 60-100 m in sunny conditions with good light.
Closer looks at this paler gull revealed that (1) the entire bill was yellow, with a clear, thick black bill band, and a concolorous yellow tip. Although very rarely third winter (?) and adult Kamchatka Gulls seem to show a similar bill pattern, first summer Kamchatkas invariably show a pinkish or dull bill without a clear band or yellow tip. In addition, (2) the structure was rather more powerful than the other Kamachtka Gulls, the bird being deep and heavy-breasted, with a less peaked crown. (3) The mien was also aggressive, though "sleepy", with deep-set eyes set off by a whitish eyering. The upperparts were (4) a clear shade of grey paler than the other Kamchatkas, even when the birds moved angle, though the coverts appeared to be washed faintly brown. (5) The tertials were extensively and contrastingly dark (clearly suggesting it should be aged as a first summer), and effectively lacked a pale fringe (another supporting character for Ring-billed). (6) The primaries were dark, with no white or whitish primary tips visible (again suggesting first summer). The head was (7) mainly whitish and only faintly mottled with brown, though heavier markings were concentrated on the nape, spreading down onto the nape sides. The underparts were white. (8) The legs were yellow and dull, tinged very slightly greener. First summer Kamchatka Gulls should show pinkish or grey-toned legs, not yellow or yellow-green. The eye colour was dark, similar to the Kamchatka’s.
In flight, the bird appeared (8) clearly larger and longer-winged (estimated at the time to have a wing length 5-8% longer than the accompanying Kamchatkas), with a slower and more leisurely wingbeat. It showed extensive blackish on the outer primaries (extending up onto primary coverts, a feature sometimes shown also by Kamchatka Gulls), with one very small white mirror just visible on the underside of the primaries (Primary 9?), confusingly suggestive of a more mature plumage. The secondaries showed a broken black bar, apparently edged obviously whiter (most obvious on the outermost secondaries), though this could have been partly an effect of the light, while the coverts looked grey-brown and a little worn (though not nearly as worn and faded as is often the case on Ring-billed).
The tail showed a broad, slightly broken black tail band, with white outer tail feathers.
Experience of Ring-billed Gull includes several visits to the US and Canada (with many hundred thousands seen), and several individuals watched well in the UK during the 1980s.
Experience of Kamchatka Gull (and other East Asian larids) has been extensive since 1990.
Although the Ring-billed Gull has not yet been officially added to the OBC checklist, the species has been increasing rapidly in much of its North American breeding range in recent decades and the species has become rather regular in Western Europe. Several claimed individuals in Japan in recent years also culminated with one or two different adults photographed in Honshu, Japan in the 2001/2002 winter. (Koji Tagi in lit), suggesting that the species might become more regularly recorded in northeast Asia in future years.