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Big Gulls in Taiwan

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Old Wednesday 15th February 2017, 11:45   #1
SteveMM
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Big Gulls in Taiwan

Rather than continually badger those (very helpful) guys over in the Q&A, I thought I'd start a thread here to present some of the bigger gulls (problem or otherwise) that I'm coming across whilst living in Taiwan.

I'll start with the attached photo (taken this afternoon), in which most of the taxa that occur can be found: taimyrensis, mongolicus, vegae, and a very nice vagrant Great Black-headed Gull.

I'm far from a novice birder, but for many years have chosen to overlook many aspects of identification where this tricky group is concerned, opting instead to tick the 'easy' ones and move quietly on. In starting this thread, I'm hoping to now fill all those embarassing gaps in my knowledge of this 'set' and would sincerely appreciate being told whenever I'm getting things wrong (or any input whatsoever for that matter).

Steve
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Old Wednesday 15th February 2017, 12:05   #2
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It makes sense to start with the most numerous of the wintering taxa: taimyrensis (whatever that means). I'm under the impression now that this 'form' is being treated as a 'hybrid swarm' (between heuglini and vegae), hence characteristics of either of the two ancestral parent species could conceivably be evident in any given individual taimyrensis. This form does seem to be remarkably variable.

My chief target with the camera today was a very dark (so lots of heuglini in it) first-winter taimyrensis that has been hanging around Chiayi. Malling Olsen and Larsson states (for heuglini) that juvenile plumage is retained until very late (December). It also states that grey feathers of an 'adult-type' or of a 'first-winter-type' can replace juvenile feathers in the moult to first-winter. Many of the new feathers apparent in the mantle and coverts of this bird seem to be of a very dark grey.

Attached: First-winter taimyrensis (ID'd by uniformly solid dark greater coverts, absence of pale window, contrasting unmarked white uppertail, active moult to first-winter).
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Name:	Heuglin's Gull (03) - Copy.jpg
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Old Wednesday 15th February 2017, 12:21   #3
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Birds as dark as the one above do not seem typical at this time of year, and the more typical individual is one of a rather greyish type. The bill colour (i.e. the presence or absence of pink) seems extremely variable and unreliable as any kind of ID feature.

Attached: First-winter taimyrensis (ID'd by uniformly solid dark greater coverts, relatively indistict pale window, contrasting unmarked white uppertail, active moult to first-winter (in mantle)).
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Name:	Heuglin's Gull (07) - Copy.jpg
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Old Wednesday 15th February 2017, 12:27   #4
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Even more advanced first-winters show bicoloured bills. The individual below is replacing its innermost greater coverts with feathers of an 'adult-type'. Such individuals do confuse me, as they rather resemble second-winters of some of the larger taxa. However, slender build seems to make them taimyrensis and pointed outer primaries makes them first-winters.

Attached: First-winter taimyrensis (ID'd by uniformly solid dark greater coverts, relatively indistict pale window, contrasting unmarked white uppertail, active moult to first-winter/first-summer).
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Old Wednesday 15th February 2017, 12:32   #5
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Another type can be altogether more frosted and whitish, but they remain taimyrensis (http://www.birdforum.net/showthread.php?t=339697). It appears as though the individual below has also replaced its innermost greater coverts, only this time with feathers of first-winter type. (It's going to look just astonishing when it has finished moulting those!)

Attached: First-winter taimyrensis (ID'd by uniformly solid dark greater coverts, relatively indistict pale window, contrasting unmarked white uppertail, active moult to first-winter).
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Name:	Heuglin's Gull (01) - Copy.jpg
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Name:	Heuglin's Gull (02) - Copy.jpg
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Name:	Heuglin's Gull (03) - Copy.jpg
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Old Wednesday 15th February 2017, 12:36   #6
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Thus ends my first 'blitzkrieg' posting of first-winter taimyrensis gulls. As I said higher up, I am desperately trying to learn about these things, so please do feel free to point out any errors (either in identification or in ageing). Many more gulls yet to come!

Steve

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Old Thursday 16th February 2017, 01:11   #7
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More immature taimyrensis. First, another first-winter. I have no idea quite what's going on with this one!

Attached: First-winter taimyrensis (ID'd by uniformly solid dark greater coverts, relatively indistict pale window, contrasting unmarked white uppertail).
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Old Thursday 16th February 2017, 01:27   #8
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Second, a second-winter taimyrensis. I'm on much shakier ground with later immature plumage stages of all these gulls and struggle immensely with anything that's not a first-winter or an adult. That said, I believe Mongolian of same age would be browner, have larger window and complete tail band. Third-winter Mongolian would have more extensive grey above and no brownish feathers in upperwing coverts. At both ages, there should be no mirror on P10.

Attached: Second-winter taimyrensis (ID'd by uniformly adult mantle, mix of adult and juvenile-like feathers in upperwing coverts, distinct but restricted pale window, mirror on P10, broken tail band).
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Name:	Heuglin's Gull (10) - Copy.jpg
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Old Thursday 16th February 2017, 10:09   #9
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I've struggled to find immature mongolicus in this recent period of looking, coming across a mere two first-winters. Thanks to some help from the guys in the Q&A, I now feel a lot more confident when separating these from taimyrensis .

Below is one (left bird) sat with a first-winter taimyrensis (right bird). It has long since completed replacing its scapulars, which are a very pale grey-blue and lightly/weakly (but black) marked. These feathers are much newer than the wing coverts, which are lightly patterned with reddish-brownish markings but overall look whitish (they are bleached). There are also no signs of feather replacement within these feather tracts.

An obvious contrast between newish first-winter scapulars and old retained juvenile wing coverts seems to be a very good feature to use to pick out first-winter mongolicus.

Attached: First-winter mongolicus (ID'd by uniformly pale blue-grey (and poorly-marked) scapulars which contrast with predominantly white (bleached) retained juvenile coverts and no evidence of feather replacement).
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Old Thursday 16th February 2017, 10:27   #10
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A second bird on a different day in flight, providing a chance to look at the wing.

The contrast between the scapulars and upperwing coverts is obvious (though surprisingly much of the mantle looks juvenile). Unlike taimyrensis, there's no solid dark bar across the outer greater coverts and (although patterned) these look predominantly white and contrast strongly with the secondaries. The trailing edge is broken by a wide white stripe formed by the tips of P1-4, and these contain dark 'arrowhead' markings. The pale in this area forms a prominent window. Additionally, much of the outer wing looks a lot browner (faded) than it does on taimyrensis, suggesting the feathers are older.

Attached: First-winter mongolicus (ID'd by uniformly pale blue-grey scapulars (with narrow markings) which contrast with predominantly white (bleached) retained juvenile coverts (as do secondaries), white trailing edge P1-4 (and prominent window), older brownish-looking outer wing, and no evidence of feather replacement).
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Name:	Mongolian Gull (01) - Copy.jpg
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Name:	Mongolian Gull (03) - Copy.jpg
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Old Thursday 16th February 2017, 11:12   #11
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And a second bird taken on the same day as the flying individual above. I believe this to be mongolicus, too, but in many ways it is rather cryptic.

Unlike the individual above, the wing coverts seem to be in very good condition and show no signs of wear. There is also a brown bar through the greater coverts, though this is diffuse and pale. However, on the rest of the wing, it is similar to the individual above, with a large window, a pale trailing edge to P1-4, and contrastingly brownish and faded primary coverts and outer primaries. It is difficult to tell on the flying bird just what is happening in the mantle and scapulars. They seem to have been replaced, but by feathers of a different type to those of the first individual.

As I only found two mongolicus this particular day, I assume this second individual to be the bird standing in the final photo attached below (by extensively pink bill base). It is clearly mongolicus when the wing is all folded up.

Attached: First-winter mongolicus (ID'd by predominantly whitish look throughout the wing coverts, white trailing edge P1-4 (and prominent window), older brownish-looking outer wing, and no evidence of feather replacement).
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Name:	Mongolian Gull (11) - Copy.jpg
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Last edited by SteveMM : Thursday 16th February 2017 at 11:15.
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Old Friday 17th February 2017, 00:01   #12
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And here's a puzzle gull. It is most certainly either mongolicus or taimyrensis. My favoured candidate for this is now taimyrensis. Despite the strong contrast between the black subterminal band on the adult P5 and the grey base to the feather (which suggests a pale-end taxon), the shape and extent of the neck streaking looks better for taimyrensis. I also think that an adult primary and a tail band would not co-occur on a mongolicus.

This was comfortably the biggest gull amongst the thirty or so present today. I have no explanation for the pattern of feather replacement on this bird (though take it to be a second-winter on account of all the first-winter feathers still present in the upperwing), which seems to me to be entirely random!

Attached: First-winter Larus SP.
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Name:	Mongolian Gull (33) - Copy.jpg
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Old Friday 17th February 2017, 11:16   #13
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I was hoping for more first-winter mongolicus today, and got lucky with a total of three, two of which were willing to be photographed.

The first of these was a stunning and outrageously bleached individual. After some problems with the mongolicus/taimyrensis pair, it really was nice to come across a bird which fit my 'Gestalt' of mongolicus perfectly.

Attached: First-winter mongolicus (ID'd by predominantly whitish look throughout the wing coverts, white trailing edge P1-4 (and prominent window), older brownish-looking outer wing, and no evidence of feather replacement).
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Name:	Mongolian Gull (09) - Copy.jpg
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Name:	Mongolian Gull (07) - Copy.jpg
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Name:	Mongolian Gull (06) - Copy.jpg
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Old Friday 17th February 2017, 11:27   #14
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The second bird was the more 'cryptic' mongolicus from above (#11). This bird is a better fit for mongolicus than anything else when stood, but its greater coverts are surprisingly fresh-looking (though still predominantly whitish). Its tertials are also well-patterned and do appear bleached, though the primaries are blacker-looking than I would have otherwise expected.

Attached: First-winter mongolicus (ID'd by predominantly whitish look throughout the wing coverts, white trailing edge P1-4 (and prominent window), patterned and bleached-looking tertials, and no evidence of feather replacement).
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Name:	Mongolian Gull (01) - Copy.jpg
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Old Friday 17th February 2017, 11:39   #15
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There were also rather more first-winter taimyrensis around to play with than on previous visits today, including one grotesquely large-billed individual.

Attached: First-winter taimyrensis (ID'd by uniformly solid dark outer greater coverts, relatively indistict pale window, contrasting unmarked white uppertail, active moult to first-winter (in upperwing coverts and seemingly in greater coverts, in which inners look rather longer than outers).
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Name:	Heuglin's Gull (01) - Copy.jpg
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Name:	Heuglin's Gull (02) - Copy.jpg
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Name:	Heuglin's Gull (03) - Copy.jpg
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ID:	615414  
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Old Friday 17th February 2017, 13:35   #16
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Were I reading this thread (and I really hope this is of interest to someone), I would be wondering where the other species are! They are yet to come! The photos above have all been taken at one site, and this is a freshwater site slightly off the coast. Both Vega Gull and Slaty-backed Gull strongly favour the coast, so I'll need to look at them later (I do also have a coastal gull site). Mongolian Gull especially has a marked preference for freshwater sites, and is the main regular at my 'off the coast' site (but scarce at my coastal site). Whilst immatures are currently proving to be scarce, it's much easier to find adults.

Despite enormous variation in the appearance of adults (especially in eye and leg colour, but also in size and structure), 'classic' Mongolian Gulls are straightforward to identify at this time of year. They are entirely white-headed, have pale grey mantles, a large amount of black on the wingtip (with two mirrors), a pale grey tongue down the underside of P10 (about half its length, give or take), and have competed their primary moults. They are in peak breeding condition right now (as also evidenced by their very bright bills) and look quite beautifully 'soft'. Attached is a fairly typical adult.

Attached: Adult mongolicus (ID'd by completed primary moult, entirely white head, relatively pale mantle, contrasting black wingtip with largely black P10-8 and two mirrors, pale greyish hand (from below), broad white trailing edge, and bright yellow bill).
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Name:	Mongolian Gull (01) - Copy.jpg
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Name:	Mongolian Gull (02) - Copy.jpg
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Old Friday 17th February 2017, 13:57   #17
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Disappointingly, my 'off the cost site' is not really a good one for photographing gulls on the ground, so I have only managed a few rather distant shots of mongolicus so far this spring. That said, I have managed some. The attachments show the 'soft' look that mongolicus seem to have right now, a small and almost Common Gull-like individual, and the long call posture (I do keep waiting for one to open its wings when it does this, but no joy so far).

Attached: Adult mongolicus (ID'd by completed primary moult, entirely white head, relatively pale mantle, contrasting black wingtip with largely black P10-8 and two mirrors, pale greyish hand (from below), broad white trailing edge, and bright yellow bill).
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Name:	Mongolian Gull (02) - Copy.jpg
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Name:	Mongolian Gulls (01) - Copy.jpg
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Old Friday 17th February 2017, 14:15   #18
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And before I go to bed, a few more shots of adult mongolicus flying around. Almost anything is possible in that wingtip! The last bird is 'streaky wingtips', a bird that gave me a fright a couple of weeks ago! (http://www.birdforum.net/showthread....86#post3521286)

Attached: Adult mongolicus (ID'd by completed primary moult, entirely white head, relatively pale mantle, contrasting black wingtip with two mirrors, pale hand (from below), broad white trailing edge, and bright yellow bill).
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Name:	Mongolian Gull (01) - Copy.jpg
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Name:	Caspian Gull (02) - Copy.jpg
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ID:	615427  
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Old Saturday 18th February 2017, 14:13   #19
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Whilst adult mongolicus is straightforward, adult taimyrensis can be anything but. As the taxon has a more northerly distrubution, adults (or near-adults) still in primary moult in February are most likely taimyrensis (if they are not vegae). Attached are, firstly, two adults (or near-adults), both of which have yet to complete P10. They have mid-dark grey mantles, the 'correct' amount of head streaking (a dirty collar), fairly bright yellow bills, and yellow legs (which are more pinkish during winter).

The second individual shows the wing. The form typically has one mirror P10 (but regularly also has a second mirror P9), a predominantly dark P10 (from below) with typically a very short tongue which is diagonal in shape, and a darker grey underside to the 'hand' in flight.

The last two photos show an adult or near-adult in flight, and the same plumage details as outlined above.

Attached: Adult taimyrensis (ID'd by incomplete primary moult, mid-dark grey mantle, dirty collar, single mirror P10, poorly contrasting black wingtip, dark grey hand (from below), underside of P10 with short diagonal tongue, and fairly bright yellow bill and legs).
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Name:	Heuglin's Gull (05) - Copy.jpg
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Name:	Heuglin's Gull (21) - Copy.jpg
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Name:	Heuglin's Gull (22) - Copy.jpg
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Old Saturday 18th February 2017, 14:31   #20
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Some taimyrensis have already entered breeding plumage by February (having completed primary moult and lost all head streaking), and these birds can be very challenging to separate from mongolicus (especially if the light conditions are not conducive to determining mantle shade). Most taimyrensis are pale eyed and lack the beady-eyed look of mongolicus.

The photos below contain (first photo) three taimyrensis and two mongolicus, and (second photo) five taimyrensis and three mongolicus.

Attached: Adult taimyrensis (ID'd by mid-dark grey mantle, dirty collar (in some), larger more rounded eye than mongolicus, and fairly bright yellow bill and legs).
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Name:	Heuglin's Gull (03) - Copy.jpg
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Name:	Heuglin's Gull (06) - Copy.jpg
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Last edited by SteveMM : Saturday 18th February 2017 at 14:39.
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Old Saturday 18th February 2017, 14:37   #21
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One more very straightforward taimyrensis for good measure.

Attached: Adult taimyrensis (ID'd by incomplete primary moult, mid-dark grey mantle, dirty collar, single mirror P10, poorly contrasting black wingtip, dark grey hand (from below), underside of P10 with short diagonal tongue, and fairly bright yellow bill and legs)
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Name:	Heuglin's Gull (05) - Copy.jpg
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Old Sunday 19th February 2017, 13:46   #22
SteveMM
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As I'm now able to recognise many of the individuals at my freshwater site, this probably signals that it is time to leave this spot alone and start spending more time at my saltwater one. I've put in so much time here as I was determined to fully get to grips with first-winters of taimyrensis and mongolicus, and never really managed anything more than acceptable photos of the latter. I only found the one today; it never came close and the light was awful all day long.
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Last edited by SteveMM : Sunday 19th February 2017 at 13:52.
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Old Sunday 19th February 2017, 13:48   #23
SteveMM
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As usual, plenty of taimyrensis present.
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Old Sunday 19th February 2017, 13:50   #24
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And to close this part, a couple of taxa that don't present any real problems on the ID front!
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Old Monday 20th February 2017, 11:53   #25
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Hi Steve...that's a wonderful set of pics and an Amazing documentation!!

I pretty much agree wwith your ID's, but not sure about bird number 4 and 6 being a tyamirensis. Aren't them too advanced in coverts moult and with pale panels on inner web?

I'd ask you to post all of this wonderful documents on Facebook. The Group is: Western Palearctic Gulls (But oriental/japanese gulls are welcome too)

You will get much more attention and replies there! It looks like here your pics are a little ...you know..hidden !
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