Over the last severa; winters we have seen birds we have suspected could be Vega Gulls (Larus [argentatus] vegae), an Siberian breeding species which winters commonly in Japan and the Pacific coast of Asia. For comparative information have a look at the photos by the Ujiharas from Japan.
The Vega Gull would become a different species from the American Herring Gull upon the split of smithsonianus, which is warranted based on at least two independent genetic studies. Below are photos of the latest two candidates for this form (species?) photographed in Half Moon Bay. Previous candidates can be seen here.
Alvaro Jaramillo 2007.
March 13, 07 - Venice Beach. I was out looking for Slaty-backed Gulls with no success today, when this adult Herring type gull caught my attention. The most noticeable feature of the bird was its slim look, long-necked and appearing to hold the front of the body up high, and the wings down low. I assumed that this was just a funny alert position that the bird held, but even after flying and landing elsewhere it still held its body consistently like this. I don't know if that has any significance, but it is the first thing that stood out about the bird. As well it showed a flat forehead, reminiscent of some of the Old World Gulls such as fuscus Lesser Black-backed, heuglini etc. Again, that is neither here nor there, but it was present. Upon closer study I saw that for a Herring Gull this bird was rather dark on the upperparts, even in intense unfiltered sun at noon. Overcast weather would have been better for assessing the upperpart colors, but in direct comparison it looked like the same darkness as a couple of nearby Western x Glaucous-winged hybrids, that is to say darker than a Glaucous-winged, but paler than a Western. The other thing that was immediately noticeable in the binoculars was the very red orbital ring, almost like on a California Gull!
Below is a photo of the bird showing the front-high stance, the general back tone and relatively large size. As well its head was nearly spotless, but clean and neat streaks remained on the nape and back of the neck. The legs were bubblegum pink. Also note that just beyond the tertials is a little half moon shaped white pattern, reminiscent of a Slaty-backed Gull. This means that this bird has pale "tongues" between the gray primary bases and black tips. A feature that is associated with Vega Gull.
Below a closer shot of the bird, the reddish orbital is visible on my screen, actually looking deeper red in the field than the red of the gonys. Eye color is variable on Vega Gull, but a dark eye would have been better than the very pale eye shown by this bird, but again, this is variable. The sleek look of the bird is apparent here. Perhaps most interesting was that the tertial and scapular crescents were large, and really stood out on this bird, much more so than on your average smithsonianus. In addition the white tips to the primaries were large as well, and the primaries looked afully fresh. They looked like they had grown in yesterday, in contrast to the more worn looking primaries of adjacent Western Gulls. On the standing bird I could also see that the mirror on P10 was large and united with the white tip, to show an entirely white primary end with black "notches" near the tip, where the black division would have been had the mirror been smaller. A hint that there could be a mirror on P9 was also visible in the field. Our West Coast Herring Gulls tend to have a mirror on p10, and rarely, rarely have one on P9. This is not the case in the east of the continent, where Herring Gulls routinely show two mirrors on the primaries. As well, our West Coast Herrings do not show large P10 mirrors that unite with the tip.
I waited for the bird to fly, and sure enough I was able to confirm mirrors on P9 and P10, as well as an extensive "string of pearls" pattern due to the white tongues dividing the black primary tips from the grey bases. This can be seen in the shot below. There is black on primaries P5-P10. As well the trailing edge of the secondaries is very wide and bold.
Below a distant shot that confirms that this bird had substantial dark on the underwings, unlike may of the odd hybrids one gets here (Herring x Glaucous-winged, Herring x Glaucous etc.).
In summary, the red orbital, dark upperparts, mirrors on P9-10, wide trailing edge, tertials crescent and scapular crescent, and string of pearls pattern on this Herring type gull suggests to me that it was a Vega Gull. This is perhaps the best adult Vega I have seen yet, although a dark eye would have been nice.
Feb. 21, 2006. At about 4:30 pm, while looking for Slaty-backed Gulls found by Ron Thorn and Dan Singer earlier today (no luck) I saw this candidate for Vega Gull. Initially the bird reminded me of California Gull due to the size, the dark mantle, bicolored bill and streaking denser on back of neck and breast sides than midline of breast. But quickly that thought left my mind, as this bird had pale eyes and pink legs. The mantle was distinctly darker than that of Glaucous-winged Gulls, and in some lights looked only slightly paler than Western Gull. I did not have it beside a California Gull at any time, but the mantle shade was similar to that. Structurally this bird reminded of a smithsonianus Herring Gull, but it was slimmer and the bill was quite parallel sided. In these respects it was tending towards California Gull. The legs were bright pink, with a more purplish tone than Western Gulls. There is a good article by Chris Gibbins on surfbirds about identifying adult Vega Gulls, and much of it is applicable to third cycle birds.
Below, another shot, showing the California Gull look to this bird. The bill pattern and streaking pattern also recall a Black-tailed Gull, although this bird was paler on the upperparts, and lacked a solid colored tail. The strikingly bicolored bill is a pattern common in some smithsonianus Herring Gulls, but usually in the first or second cycle, not the third cycle. By this age, the black is reduced on the upper mandible, and you tend to get more red coming in on the lower mandible.
Below the bird is sandwiched between Western Gulls, it is obviously paler in this angle, but the difference in mantle shade is less than would be expected if the bird was a smithsonianus Herring Gull, which are silvery gray above.
Below, a close up of the face. Two features are important, first of all the orbital ring is reddish. Our smithsonianus Herring Gulls typically show orange orbital rings, red orbitals are usually a good sign of Thayer's, but this bird is not one of them. Vega Gulls do show reddish orbitals, like the bird in question. The other issue is that the eye is not pale yellow, as would be expected on a smithsonianus Herring Gull but it is flecked with dark. This could be explained by the age of this bird, but typically smithsonianus show adult like eye colors by the third cycle, in fact it typically shows up in the second cycle.
In flight there was a mirror on P10, none on P9, and black on the outer 6 primaries (to P5). The black on the primaries may be a bit less extensive than on average Vega, but within what is normal based on what I have read. The small pale tongues at the interface of the gray primary bases and black tips are also typical of Vega, not classic of smithsonianus, and this bird showed them. The tail was largely white, except for a remnant dark tail band.
Below is another flight shot, the pale tongues just inside of the black primary tips can be seen. A mirror on P9 would have been a better wing pattern to differentiate from smithsonianus, but a single mirror on P10 is still common in Vega apparently.
Feb. 15, 2006 - A darker individual than the Feb. 11 bird, but very similar. Differences can be seen in the tertial pattern, and in particular in the less extensive white of the tail of this bird. Even so, it showed a clearly pale tail base, tail coverts and rump, contrasting with a broad dark tail band. Also features that suggest vegae are the well marked greater coverts, being banded all the way out to the end on this bird. Like the Feb. 11 bird, this one was almost entirely in juvenal plumage although this individual did show some new (formative/first basic) upper scapulars. The delayed molt and similar look of both birds, is quite unlike that of most first cycle smithsonianus individuals in the flock. Note also the pale inner primary window, typical of vegae and smithsonianus, and the blackish outer primaries and tail band suggesting this is not a hybrid with a pale-winged species.
Below a profile of this bird, a slightly shorter billed individual than the Feb. 11 bird. The structure is similar to that of a smithsonianus, as was the size. Visible here is the largely juvenal plumage, well banded greater coverts, and finely notched and largely dark tertials.
Below an open wing shot, showing the tail pattern a bit better. I wonder if the extensively dark wing linings are a feature that could help separate some vegae from some argentatus/argenteus??? Classic smithsonianus is dark on the wing linings during the first cycle.
Below, the new upper scapulars can be seen, each appears gray with an anchor pattern. The classic smithsonianus formative/first basic scapulars are brownish-grey with a paler edge, anchor patterns are not the norm, although they can show up more commonly in second cycle birds. The darker look of this bird is much more similar to many smithsonianus, but the extensive pale banding on the coverts were distinctive enough to draw my attention. Perhaps birds like this are at the limit of where the identification of vegae and smithsonianus is possible (if you believe its even possible at all!).
Feb. 11, 06. This bird was found by David Vander Pluym in the Venice Beach flock, Half Moon Bay, San Mateo County, California.
Below is a flight shot, like smithsonianus Herring Gull, Vega Gull has a pale inner primary window, separating it from Lesser Black-backed Gull and relatives such as Heuglin's Gull. The dark outer primaries and secondaries contrast strongly with the pale inner primaries. The most striking feature, which separates it from smithsonianus, is the extensive pale rump and uppertail coverts as well as pale tail base with broad dark tail band. On this bird, the tail band can be seen to narrow on the outer rectrices. Here are some flight images of Vega for comparison, from the Ujiharas, in Japan.
Below, the bird preens showing a detailed view of the very restricted amount of dark on the outer tail feather, as well as the pale base to the tail. The greater coverts are widely banded with pale, and the banding is strong right to the wing bend. Typically on smithsonianus, banding on the greater coverts decreases outward such that the outer greater coverts are decidedly dark based. The tertials of this bird are dark and notched pale, lacking a broad white tip as on species such as Slaty-backed Gull. The primaries are blackish, not brownish. The contrastingly dark tail band and primaries are a point against any hybrid with a pale species such as Glaucous-winged Gull or Glaucous Gull, not that any of those hybrids look like this, but in case the question of smithsonianus x Glaucous-winged Gull is going through people's thoughts, I think this feature and the overall appearance makes that an unlikely scenario for this bird.
Below, a close up in flight showing the broad dark tail band, pale tail base, contrasting whitish rump and uppertail coverts. The banded greater coverts extend well out on the wing, and the pale inner primary window is seen here.
Below, the bird perched. The white background to the body plumage, nicely streaked head, contrastingly barred upper and undertail coverts, and generally checkered appearance gives the North American gull watcher a general impression of an Old World gull. The structure (not slim and very long-winged) as well as features of the coverts as well as inner primaries exclude Lesser Black-backed Gull as an identification for this bird. The individual is still in full juvenile plumage, suggestive of an Arctic breeding provenance. I don't know about the molt timing of Vega Gull specifically, but the Olsen and Larson Gull book note that "many still show juvenile plumage Feb." The molt timing therefore appears to be later than that of the average smithsonianus, but there are some first cycle smithsonianus are quite late in their molt. It is interesting as well that this late molting juvenile is still so fresh at this late date in the winter. I think that this is due to the fact that Arctic breeding species, which have the late molting strategy develop a strong and "well built" juvenal plumage, perhaps something that can only be done in the highly productive Arctic Summer.
Below is a back view, showing the scapular pattern (very nice holly leaf pattern) and the notched tertials.
Below another side view, the strongly banded greater coverts are obvious, and the crisply streaked head and neck. The masked appearance is unusual, I don't know if this is typical on Vega, but it is not typical in smithsonianus. The bill is dark, but in this strongly lit situation, the pale that is starting to appear at the base is obvious.