Caspian Gull in Mie?

To round off a pretty good day's birding in Mie on Sunday I decided to check out the 'gull beach' on the north side of Tsu city. When I arrived there were very few gulls there but a small gathering near an outfall looked promising so I sat and waited to see what might drop in. Before long a striking immature gull fetched up and spent about 30 minutes with the other gulls before heading out into Ise Bay.

Watching the bird I was struggling to think of any local gulls, either 1CY or 2CY, that could show the combination of features I was seeing. Though in fact it seemed fairly obvious that this was a 1CY. Caspian Gull Larus cachinnans cachinnans (something I've never seen) was the only thing I could think of that could show a bold dark greater coverts bar with a second generation saddle this early in the winter, particularly with the scapulars predominantly grey. Heuglin's Gull L.h.taimyrensis looks very similar in some respects, structurally far more similar than anything else we get here, but it rarely replaces more than just the odd scapular until moult really picks up in January and it wouldn't be as advanced as this bird until mid- to late March. In any case the new scapulars are initially very dark before fading to silvery with heavy anchors and bars. From what I could vaguely remember reading of Caspian there seemed to be one or two other supportive features but because of its rarity in Japan, unreliable memory and the casual way I'd found it didn't really believe it could be.

After going through the images at home there are certainly some features favouring Caspian, notably the combination of early saddle moult and resulting pattern of the next generation feathers along with a dark greater coverts bar which is impossible to account for in a Japanese context. But others cast doubt and the more look at the images the more doubt creeps in. In particular I'm worried about the depth of the bill and prominent gonys, the heavily marked underparts and relatively extensive head streaking, also I'm uncertain whether the primary projection is long enough in relation to the tail.

As the OSJ place mongolicus within cachinnans Caspian Gull is considered a winter visitor to Japan. However L.c.cachinnans isn't listed in the most recent edition (2012) of the OSJ Check-List of Japanese Birds, though there have certainly been claims in the past, so it would be a major rarity if confirmed in Japan.

Other birds which need to be considered in a Japan context are Mongolian L.(cachinnans) mongolicus and Vega L.vegae, though there's always the hybrid angle too, especially when Slaty-backed L.schistisagus influence can produce some odd-looking gulls.

With adult Vegas. The proportionately small and contrastingly white head, proud chest, flat back, attenuated rear, long primary projection and very long legs all look suggestive of Caspian Gull. Though taimyrensis can look very similar to this in both structure and overall colouration, it would be slightly shorter-legged with the wing-tips closer to the ground. The light is very dull but the central breast/belly too dark for cachinanns?

It stands very tall behind Vega however this due solely to the leg length, as can been seen in the shot below, when on water it all but disappears behind Vegas' greater bulk. In this view the head is darker and it seems fine streaking looks way too extensive for cachinanns, the fine streaks are real but the dark-headed appearance here is misleading.

At times I felt the bill looks too massive for cachinnans, with very pronounced gonys. Nevertheless the overall bill/head/neck proportions might be acceptable for cachinnans, the head shape looks good and is much whiter than the Vegas but is extensively streaked.

Coming a little closer it became obvious this wasn't a 1CY taimyrensis, the combination of juvenile coverts with second generation scapulars in (early) December is something I've never seen. Heuglin's taimyrensis shows a dark greater coverts bar but would still have fresh-looking full juvenile saddle at this time. 

Most scapulars are adult-like grey with narrow blackish shaft streaks and faint darker grey anchors. Some lower scapulars have sub-terminal blackish diamonds and one, in this view, has a blackish base and diamond linked by the shaft streak. This is pattern is never seen in Japan at this time of year on this age of gull. Surprisingly the bill actually looks slimmer and far more cachinanns-like here.

Juvenile taimyrensis, 13 November. This taxon doesn't moult a significant number of scapulars until January.

First winter taimyrensis, 20 March. New scapulars are very dark but older feathers are silvery.

A juvenile Mongolian 13 November. I don't see many juveniles as most have already moulted before they arrive but this is typical of the birds I do see.

A fresh first winter Mongolian 14 November.  

Late winter taimyrensis left and mongolicus right, 20 March.

Vega, 24 December. 

Vega, 3 November.

The possible cachinanns viewed from the rear the scapulars give the appearance of being mainly grey with dark centre lines. The tertials are black with white tips. The brownish shawl around the base of the hind neck looks very heavy but the poor light doesn't help.

The possible cachinanns again. The underwing is surprisingly uniform as the greater coverts are unmarked and seem more or less concolourous with the flight feathers. The medians are mostly unmarked but whiter which produced a white bar in the centre of the underwing. Note the pale inner webs of the primary window showing through. 

Taimyrensis underwing in late winter, 25 March.

Mongolian underwing in late winter, 20 March (taimyrensis on left).

The possible cachinnans again. A very brief burst of late sun rendered the underwing whiter than the grey in the earlier image. Only the primary tips are contrastingly black here, even p8-10 are quite pale looking. Worryingly the crown is streaked.

Vent mostly white with a single row of bold markings around the edge, basically mirroring the upperside. The pale underside of p10 may be no more than reflective but there's clearly a suggestion of a darker tip showing through. 

At rest the tail looked black with a bold ladder effect on the outer web of t6, here the detail can be easily seen. The primaries have a pale window, the inner webs are much paler than those of taimyrensis. The pale saddle contrasting with the dark wings is remarkable for any gull in Japan at this time of year.

Late winter taimyrensis, 25 March.

Juvenile Mongolian, 13 November.

The possible cachinanns again. A very striking feature is the grey looking V up the back, this never looks as contrasting with other gulls that show it, such as Mongolian. Though it looks uniform grey here it is actually finely mottled with grey-centred feathers.

Another shot showing that remarkable pale back as it flies away.

On the water (with Common Gull) the jizz is again suggestive of cachinnans rather than our local birds.

I keep going round in circles with this bird, there are a number of things that don't sit comfortably with a Caspian identification as I believe it should look according to what I've read. I'll be on the verge of dismissing it then the anomalies kick in again. The small pear-shaped head, that the bird stands so tall but sits so small compared to Vega, the saddle which is three months ahead of taimyrensis and the different pattern to all the local gulls. The coverts bar alone rules out Vega too. Then there's the uniform underwing and pale back wedge to explain. Even by gull standards it's a strange one but depite my doubts it's closer to cachinnans than anything else.

Common (Kamchatka) Gull, adults in Japan

Common Gulls Larus canus start arriving in Osaka in mid-October, with some present till mid-April. I might see 30-40 birds per visit to the Yamatogawa (Yamato River) in Osaka during winter but daily counts number in the hundreds during March. Many over-wintering gulls associate with Black-headed Gulls Chroicocephalus ridibundus on the river but most, especially during migration, only spend a short time on the river each day, dropping in to bathe, preen and loaf before heading back out into Osaka Bay. Many easily recognisable individuals are rarely seen more than once indicating a high turn over during passage and suggesting a huge number of gulls could be passing through the region during March. Some also winter on Lake Biwa making it the only taxon other than the widespread Black-headed Gull that can be reliably found away from the coast.

Many people comment on the bewildering difference in size and structure between the largest, most robust gulls and the very small delicate birds. The largest approach small Vega and the smallest aren't so much bigger than Black-headed. The big questions are if, or more likely how many heinei occur, how much of a potential problem kamtschatschensis x heieni intergrades might be given their apparently extensive overlap in breeding range according to GULLS (Olsen et al) and whether this potential presence blurs any morphological boundary that might otherwise be more apparent between the two taxa? Additionally, there are many claims of Mew Gull L. brachyrhynchus in Japan and while they might be expected to occur would any other than the most extreme individuals even attract attention? I have plenty of questions and no answers, the images below show some of the variation I see in Osaka.

The obvious starting position that the largest, heavily built birds are kamtschatschensis is hard to argue with but any expectation that the smallest, lightly-built are birds good contenders for heinei doesn't follow. There's no shortage of mini-kamtschatschensis around as the presence of a small number of apparent 1CY heinei compared to the large number of equally small very dark 1CY/2CY kamtschatschensis attests. But when it comes to adults it doesn't seem possible to differentiate between them. The additional problem of the potential intergrades, which isn't possible to prove one way or the other, means an unknown number of birds below might not be kamtschatschensis. Starting with saddle shade, there's quite a bit of difference between the lightest and darkest though the very darkest aren't common.

November 23. An obvious kamtschatschensis with three Taimyr Gulls (part of a flock of about 30), the large size and very dark saddle of this individual leave no doubt about this gull.

February 12. Quite a range of saddle tint here, the gull on the left is another example of the uncommon very dark individuals.

March 25 (above) and 31 (below). Less contrast between these two respective pairs, it's no more than coincidence that six days apart the upper duo have stronger bill markings and more complete non-breeding heads.

Moving on to the non-breeding foreparts, obviously earlier in the winter head markings are more prominent, they are variable in extent and intensity but are reasonably consistent in basic pattern. Usually the feathering along the bill is unmarked, the crown finely streaked often with denser markings around the eye and/or ear coverts, the hind neck becomes more spotted compared to the crown and this frequently coalesces into a smudgy base. Below is a range of head, neck and breast patterns, some less common than others but none can be considered unexpected if spending any time watching these birds.

December 4. Two fairly heavily marked with typical patterning, one with a narrow bill band and the other unmarked. 

December 4. A typical bird in the background and a heavily marked gull in front. The feathering along the top of the bill is often combined with darker, denser than usual markings elsewhere on the head and neck. Taimyr Gull on the right.

March 17. Another dark gull on the left, such extensive breast markings are less common.

February 14. The neck and breast markings are more extreme on this one.

 January 24. Dark heads render eye crescents more prominent where they exist but, unlike this gull, many don't show this feature.

January 22. So far the gulls shown have heavily peppered dark-looking eyes but many are more lightly marked.

January 22. Bill markings are variable but some have complete rings. This bird is probably a third winter judging by the smaller, worn apical spots, though often birds of this age have distinctly greenish bill and legs.

December 24. The gull on the right is also probably a third winter and again has a complete bill band and also very small A-spots and green legs.

January 17. A much more delicate bird but the markings are quite typical of kamtschatschensis.

February 14. The clearly spotted hind neck and side of breast is notable compared to the usual smudgy appearance.

April 9. This gull is genuinely unusual, the combination of large head and short, stout bill along with short primary projection and exceptionally large p10 mirror give it an almost mini-Vega feel.

A lot is made of wing-tip pattern as a means of identifying the different forms of the group but birds here show such a degree of variation it seems unwise to put much faith in it. If there's such a thing as a typical kamtschatschensis the outer primaries should look something like this; p10 has a short grey wedge on the inner web angling from the base to the edge on the underside but this isn't visible on the upperside. The upperside of p9 often does show a small area of grey in the base though at a glance it seems all black, however the underside can have a grey tongue up to a third of the feather length. P8 is more variable, typically the upperside tongue is slightly longer and forms an neat continuation from p9 across the outer wing, on the underside it is frequently two thirds the feather length. P7 has a long tongue above and below with a prominent white tip. P6 has a broad black sub-terminal band extending a short way up the leading edge. Whereas the band on P5 is narrower and of even breadth. However there are plenty of exceptions.

The two flight shots above illustrate the typical kamtschatschensis wing tips with consistent p9-10 mirrors. The bird on the right in the lower shot has a very small p8 mirror, they are often much larger.

March 21. There's probably no such thing as a perfect example of a standard Common Gull but it might be difficult to find one closer than this, even though the p5 band is broken.

March 20. At a glance this is another typical gull but there are subtle differences from the previous gull. The broken band on p4, very narrow white tips to the inner primaries and bleeding rather than sharp divisions between the grey and black of the outer primaries are all atypical features to a certain degree but each crops up regularly. 

March 20. Another with a narrow trailing edge to the inner primaries, minimal white separators and relatively short grey tongues in the outer primaries, basically a typical "dark" bird.

 April 9 2006. An incidental video grab that appears to show a Common Gull with a white-tipped tongue on p9. Unfortunately I didn't see this bird in the field but the stretching wing really stood out watching the tape. 

March 30. A long tongue in p10; this is beyond unusual!

March 25. The bird on the left has a long p8 tongue with a long white tip terminating close to the proximal edge of the p9 mirror. The bird on the right has a shorter white-tipped tongue but it also has a prominent third mirror combining to produce a very white wing tip. Despite getting many shots of the bird in the middle, its identity remains a total mystery but getting two whiter wing-tipped gulls in the same shot by chance shows they aren't so unusual.

January 24. Most birds have the proximal edge of the p10 mirror angled towards the edge.

February 14. Some gulls have the p10 mirror proximal edge squared across the feather.

February 14. An example of a very small bird and in direct comparison the bill was no thicker but obviously shorter than those of Black-headed Gull. In flight it (below) it was very white-winged but this was mainly due to a prominent p8 mirror.

February 14. A closer example of a bird showing a bold string of pearls. Though this feature is associated with Mew Gull, it isn't rare in the Osaka population.

March 23. Comparison of wing tips, a brachyrhynchus pattern next to a typical bird.

If the above outer primaries are more associated with brachyrhynchus than kamtschatschensis, the following bird, one of two others in the same flock as the above bird, is altogether more Mew-like. It (they?) could even be Mew, if not they certainly complicate matters.

March 23. The bird in question (top right) shows much white in the primary projection because of the extremely long white-tipped tongue leaving only a narrow black sub-terminal band.

The head differs from the norm in have such indistinct markings to be largely grey-washed

While some kamtschatschensis are small-billed this bird is particularly so.

P7-8 look completely grey for most of their length with extensive white longer than the sub-terminal black which bleeds only a short distance up the edge of the outer web. The apical spots on p6-8 are noticeably small than I'm used to. The final very heavily cropped shot also shows the soft, indistinct head markings and a more pronounced choker than shown by kamtschatschensis.