THE 'HERRING GULL' COMPLEX
1. Minimalist Key to Winter Adults in Japan (Charles Harper)
I go looking for gulls once a year, on New Year's Day, at Choshi, Chiba Prefecture. The systematics of this group gives me a headache, particularly because it is always being shuffled around. Rather than worry about relationships, I have just been trying to identify the distinctive forms here. Presumably, there are six forms that could occur with any likelihood in Japan: heuglini, taimyrensis, birulai, vegae, smithsonianus, and mongolicus. There is a lot of identification literature out there, so much that I have been unable to come to terms with it, and have instead constructed for myself a minimalist key to winter adults that at least allows me to sort roughly through the madness:
1a Legs pink
2a Mantle light
3a Head streaking fine or absent; head rounded: mongolicus
3b Head streaking heavy, bibbed; head flattened: smithsonianus
3c Head streaking medium, head large, angular: birulai
2b Mantle dark
4a Head streaking narrow, heavier on nape; head flattened: taimyrensis
4b Head heavily spotted; head angular: vegae
1b Legs yellow
5a Mantle light (lighter than vegae); head streaking fine or absent: mongolicus
5b Mantle dark
6a Head streaking narrow, heavier on nape; head flattened: taimyrensis
6b Head streaking bold, heavier on nape; head small, rounded: heuglini
1. Minimalist Key to Winter Adults in Japan (Charles Harper)
I go looking for gulls once a year, on New Year's Day, at Choshi, Chiba Prefecture. The systematics of this group gives me a headache, particularly because it is always being shuffled around. Rather than worry about relationships, I have just been trying to identify the distinctive forms here. Presumably, there are six forms that could occur with any likelihood in Japan: heuglini, taimyrensis, birulai, vegae, smithsonianus, and mongolicus. There is a lot of identification literature out there, so much that I have been unable to come to terms with it, and have instead constructed for myself a minimalist key to winter adults that at least allows me to sort roughly through the madness:
1a Legs pink
2a Mantle light
3a Head streaking fine or absent; head rounded: mongolicus
3b Head streaking heavy, bibbed; head flattened: smithsonianus
3c Head streaking medium, head large, angular: birulai
2b Mantle dark
4a Head streaking narrow, heavier on nape; head flattened: taimyrensis
4b Head heavily spotted; head angular: vegae
1b Legs yellow
5a Mantle light (lighter than vegae); head streaking fine or absent: mongolicus
5b Mantle dark
6a Head streaking narrow, heavier on nape; head flattened: taimyrensis
6b Head streaking bold, heavier on nape; head small, rounded: heuglini
2. Juvenile and First Winter taimyrensis Gulls (Neil Davidson)
Asked to clarify my use of the name 'taimyrensis' when I wrote my brief December 2004 review of the Kyoto area birds, it was not something I was able to do then-- or now. I am hardly qualified to write about them, but I do have a keen interest in our gulls and indeed a long-standing interest in gulls in general. While I do not have any answers, I would like to share my thoughts and frame some questions which may stimulate debate or kindle interest in a family which is not everyone's cup of tea. After all, it is we birders active in this region who have most experience with these birds.
The position of taimyrensis is vexed: when I referred to it as such in that December review, it was simply because I did not know which common name to use for those birds. Heuglin's Gull, L. heuglini heuglini, is generally considered to be part of the fuscus group, related to Lesser Black-backed Gull, L. (fuscus) graellsii, and Baltic Gull, L. fuscus (if the latter is accorded specific rank), and with its eastern race taimyrensis comprises Heuglin's Gull. All well and good, except for a widely accepted belief in the existence of an intergrade population between Vega Gull L. vegae birulai and taimyrensis which clouds the issue and results in the supposition that yellow-legged, dark-mantled birds are L. h. taimyrensis while pinker or orange-legged birds as typically seen in Japan are intergrades. Yet another school of thought considers that the intergrades are the result of direct Heuglin's (L. h. heuglini) x Vega Gull hybridization, and that taimyrensis does not exist as a valid taxon at all.
Whatever the true taxonomic situation, it is undeniable that there is a great deal of variation, including mantle and leg colour, within the large white-headed gulls that pass through or winter in this part of the world. However, that could also be said of smithsonianus in North America or argentatus in Europe, not to mention vegae/birulai here-- even without any complicating hybridization factors. In fact, the large white-headed gulls in general show considerable variation within any accepted taxon. It may be unwise to put too much emphasis on only such variable features as mantle and leg colour when dealing with taimyrensis, a relatively little-known entity which breeds in an extensive and remote area and winters over a remarkably extensive range from Japan to as far as eastern Africa, according to several authors (Olsen and Larsson, 2003).
The large white-headed gulls are prone to a greater degree of hybridization than many families of birds. It is not difficult to imagine the situation in which a stable intergrade population could develop in a current or former area of sympatricity between two closely related species. Could heuglini and birulai (or vegae) interbreed to the extent of creating an intermediate population? Iftaimyrensis does exist in its own right, then would it not be more likely to interbreed with heuglini than birulai, assuming they come into contact? This remains no more than speculation without major research on the vast breeding grounds of continental Asia. It is tempting to draw comparisons with other gull species, the obvious being Lesser Black-backed and Herring Gulls, which, while interbreeding, do not threaten to develop an intergrade population (though the more closely related graellsii and intermedius do just that). I have no personal experience of these birds outside Japan and cannot comment on the different appearances of adults in other areas; but I believe that the majority of adults I see here would generally be thought of as intergrades, because of their superficially intermediate appearance between 'dark-type' taimyrensis and Vega, when compared to adults described elsewhere within their wintering range. I say 'superficially' because the more obvious field characteristics, mantle and leg colour, fall conveniently between the presumed progenitor species. Yet they and more important structural features are as consistently diagnostic as features shown by other normally recognized taxa. Of course a hybrid population would be expected to show a consistency, somewhat intermediate between its two progenitor species, which might suggest racial or even specific validity-- as was the case with 'Cox's Sandpiper' for many years before its true hybrid origins were discovered. But in the case of taimyrensis-types here, I cannot help but wonder if their superficially intermediate appearance might not be disguising their true status as part of Heuglin's Gull rather than being intergrades. The most compelling reason for this suspicion is the appearance of juvenile and first winter birds: not only are they clearly diagnostic, but rather than showing features of both progenitor species as they might be expected to, they look very firmly part of the fuscus group.
My intention here is only to present some images of what I believe to be juvenile and first winter birds in order to illustrate the differences between them and similarly aged Vega Gull. A major problem is that there is no way to know for certain whether these birds are, as I suspect, the offspring of 'intergrades'. Such is the difficulty of trying to determine anything on the wintering grounds, that it is even conceivable that they could be the offspring of 'true' taimyrensis wintering in a different area than the adults. My experience with juveniles is limited to the two birds shown below, discovered on the Japan Sea coast; I have never found any in Osaka. I would appreciate any feedback, correction or additional input. I cannot claim definitively that they are what I believe them to be, even though I have since seen many more first-winter birds. The following video-grabs are all of quite well-marked individuals; other individuals exist which are more problematic; it is my opinion that these represent the benchmark appearance in Japan.
But as I said earlier this is very much to promote broader discussion. For a more detailed overview of the large white-headed gulls of the region and more detailed information on identification, Nial Moores' paper "The Herring Gull Assemblage" at the Birds Korea website is recommended.
Pics 1-2: Juvenile, Nov 22
Upperparts: mantle and scapulars mostly juvenile, solidly dark with narrow, mainly even, whitish fringes and blackish subterminal fringes. A small number of first-winter feathers are present, quite dark grey with darker grey centre line and transverse bar.
Folded Wing: The wing as a whole is very dark, in keeping with the mantle and scapulars. The tertial pattern is basically similar to the scapulars but the pale fringe, as is typical, does not extend to the base, though they can be longer than on this bird (Pic 3). Birds can have completely dark-centred tertials or, like this one, show relatively indistinct internal pale areas distally on the longest feathers as can often be seen on members of the fuscus group; dark feathers like these are much less common in Vega, which usually shows a narrow dark subterminal line at the tip isolated by an extensive pale or white area (Pic 4,12) and frequently has a complete white fringe reaching the base, as well as often having white notches or indentations along its length. The greater coverts here are much darker than is typical for Vega; although some Vegas this age can show smithsonianus-like dark outer greater coverts, they are not usually as extensive as on this bird. Vega less often has such dark innermost coverts, which here look very like the scapulars and tertials; though the innermost coverts of Vega can also be darker than the neighbouring feathers, they seem more consistently barred and when dark have broader, often notched, white fringes. The lesser and median coverts are largely dark, again with neat even fringes completing the overall picture, one of dark uniformity.
Spread Wing: the dark outer wing seems typical of the fuscus-group, the primaries and primary coverts are almost uniformly blackish-brown and there is no more than an echo of the pale inner primary window shown by Vega and other Herring Gull-types. The outer greater secondary coverts are also extensively dark, forming a conspicuous dark bar in flight.
Bare parts: note that this bird is already showing a paler base to the bill while a second bird (Pic 3) also shows a pale base to the lower mandible.
Upperparts: mantle and scapulars mostly juvenile, solidly dark with narrow, mainly even, whitish fringes and blackish subterminal fringes. A small number of first-winter feathers are present, quite dark grey with darker grey centre line and transverse bar.
Folded Wing: The wing as a whole is very dark, in keeping with the mantle and scapulars. The tertial pattern is basically similar to the scapulars but the pale fringe, as is typical, does not extend to the base, though they can be longer than on this bird (Pic 3). Birds can have completely dark-centred tertials or, like this one, show relatively indistinct internal pale areas distally on the longest feathers as can often be seen on members of the fuscus group; dark feathers like these are much less common in Vega, which usually shows a narrow dark subterminal line at the tip isolated by an extensive pale or white area (Pic 4,12) and frequently has a complete white fringe reaching the base, as well as often having white notches or indentations along its length. The greater coverts here are much darker than is typical for Vega; although some Vegas this age can show smithsonianus-like dark outer greater coverts, they are not usually as extensive as on this bird. Vega less often has such dark innermost coverts, which here look very like the scapulars and tertials; though the innermost coverts of Vega can also be darker than the neighbouring feathers, they seem more consistently barred and when dark have broader, often notched, white fringes. The lesser and median coverts are largely dark, again with neat even fringes completing the overall picture, one of dark uniformity.
Spread Wing: the dark outer wing seems typical of the fuscus-group, the primaries and primary coverts are almost uniformly blackish-brown and there is no more than an echo of the pale inner primary window shown by Vega and other Herring Gull-types. The outer greater secondary coverts are also extensively dark, forming a conspicuous dark bar in flight.
Bare parts: note that this bird is already showing a paler base to the bill while a second bird (Pic 3) also shows a pale base to the lower mandible.
Pic 3. Another bird, same date
Very similar to the previous bird, showing the same basic appearance.
Pic 4. First-winter Vega, same date
This a particularly clean-looking first-winter bird and illustrates the much whiter distal area of the tertials as well as of the innermost greater coverts and the median coverts.
Pic 5. First-winter, February 26
Structure: This is a good profile shot, showing the structure to advantage. Though smaller than most Vega, they tend to be proportionately long-legged and long-winged and have a more attenuated appearance, but are short-billed compared to other 'long species', though not necessarily more so than Vega.
Pic 6. Same bird and date
Here it shows the extent of the dark greater covert bar. It has acquired second generation mantle and scapulars which, like those of the juvenile bird (Pic 1-2), are darkish-grey; but some of these are clearly white-tipped, possibly due to bleaching or wear, but perhaps they are variable in appearance just as there is enormous variation in Vega? The tertials are white-tipped and look quite different from those of the juveniles, so are also possibly second generation; but they are also fairly worn, which is perhaps a little surprising. Nevertheless, immature feathers do tend to wear and fade more quickly than those of older birds.
Pic 7. First-winter, March 21
A month later than the previous bird; this is a similarly darkish-mantled bird looking much cleaner-headed as its moult progresses.
Pics 8-9. First-winter, March 5
A much paler bird, the mantle and scapular feathers are almost totally lacking grey and as with the previous first-winter birds the tertials have broad white tips. The dark spread wing contrasts markedly with the pale body.
A much paler bird, the mantle and scapular feathers are almost totally lacking grey and as with the previous first-winter birds the tertials have broad white tips. The dark spread wing contrasts markedly with the pale body.
Pic 11. First-winter, March 25
This may be the same bird. The more distant flight view gives a clearer appreciation of the uniformity of the primaries compared to Vega, which would show a conspicuous inner primary window in this situation.
Pic 12. Vega, January 25
A dull, muddy and quite typical-looking bird compared to the clean first-winter (pic 4), showing how variable in appearance these birds can be. Nevertheless, this bird has the expected Vega inner and, as far as can be seen, outer greater coverts, plus extensive white in the tertials and more restricted dark centres to the median and lesser coverts.
(Neil Davidson, February 2005)