Adult Vega Gull

This post shows a sample of Adult Vega Gulls (Choshi, Japan, 27 Dec 09 - 4 Jan 2010). Each photo shows a different individual. Certain things are rather consistent (e.g. leg colour, orbital ring colour) but other things are very variable (e.g. iris pigmentation, pattern and extent of head streaking). While there is individual variation, to my eye the average bird is rather more evenly proportioned than Herring Gull, with a smaller head and parallel-sided bill. The post below shows flight photos, illustrating the details of the wing tip pattern of this taxon.

Adult Vega Gull wing-tip patterns

This post hopefully gives a sense of the wing tip pattern of Vega Gull. All photos were taken at Choshi, Japan, between 27 Dec 2009 and 4 Jan 2010. It is notable that a significant proportion of birds had yet to complete primary moult; this is appreciably later than argentatus Herring Gull (yesterday in NE Scotland I only saw 1 bird from approx 200 'argies' that had yet to complete primary moult). This moult difference may not be useful in a vagrant context, but is interesting nonetheless. Things to note on this sample of Vega include the pattern on P5 (ranging from no black to a full black band), the presence of black on P4 on some birds, and variation in the pattern on P10 (pattern of black and white at the tip, and the presence or otherwise of a pale tongue on the underside). Some data showing the extent of black in the primaries of Vega Gull (relative to mongolicus) and examples of various P10 patterns are presented below. These data were originally published in an article on Surfbirds, an article based on a trip I made to Choshi in February 2003

Fig 1. Extent of black in the primaries of Vega and Mongolian Gulls. Mongolian Gull data are taken from Yesou (2001).
Fig 2. Sketches showing the range of P10 patterns in Vega, ranging from maximum (top) to minimum (bottom) amount of white. The botton two are the most frequent patterns.

This individual is extreme, in having limited black (e.g. nothing on P5) and much white (long white tip to P10)

Note the P10 tongue, rather like cachinnans or L.a. argentatus. This seems rare in Vega, but as this birds shows, some have long P10 tongues.

Slaty-backed Gulls, Choshi, Japan (1-3 January 2010).

First winter. This is a very typical bird. The general plumage tones are rather uniform and the tail is wholly dark.

First winter. There is a huge amount of individual variation in 1 w birds, from very pale birds through to ones like this. All birds however (or at least the ones that I confidently identified as SBG) seem to share some basic plumage features, including the unform greater coverts, simply patterned tertials (brown with paler tip, lacking strong patterns), darkish eye mask and wholly or virtually all dark tail (i.e. very like smithsonianus).

Second winter. Second winter birds varied from largely brown individuals to ones with white bodies, grey mantle and pale, bleached looking creamy wings. This is a medium bird; its dark smudgey face is not typical - most have a darker eye mask but lack such sooty areas on the lores and chin of this bird.

Second winter. An example of a paler bird; note the very typical pale brown primaries.

Third winter. Some more advanced 2w birds look like this, but the 3rd generation primaries (blackish with small white tips) can be used to age it confidently as a 3rd w.

Adult. Unfortunately, strong sunlight made getting the correct/true-looking grey tones in this and the subsequent photo very difficult. In life, in neutral light they appear about the same grey tone as an intermedius LBB. There is some individual variability in upperpart grey tone of the birds at Choshi, with the palest birds appearing, to my eye, to be paler than intermedius but a fraction darker than graellsii. On a couple of occasions, paler and more typical individuals were seen side-by-side and the difference was quite clear.

Another adult

Mongolian Gull, Choshi, Japan.

This bird, seen on two consecutive days, fits currently accepted criteria for first winter mongolicus. I spoke to several local gull enthusiasts about it (showing them these pictures etc)and it certainly is the type of bird they are identifying as mongolicus.

Note the already worn coverts and tertials, consistent with a bird that hatched somewhat earlier than the more Northerly Vega Gull.

Striking, contrasting plumage evident in flight. Note the very black tail band contrasting with the white rump; also, it has a very contrasting pattern on the inner primaries (P1-4), with pale lozenges on the outer webs and dark arrowheads at the tip.

Rather cachinnans-like plumage tones and patterns, especially the silvery base colour and light markings on the second generation scapulars. The head and body have a white ground colour, but with greyish streaks