First-winter Larus, Chiayi County, Taiwan: Mongolian or not? (1 Viewer)

SteveMM · Jan 15, 2018

This highly distinctive (and very large) first-winter gull arrived here at least a month ago pretty much 'as is'.

I've oscillated between Mongolian and Taimyr Gull for it, but did settle on the former based on replaced (so, early) whitish scapulars (which also show some signs of wear) contrasting with much older and slightly worn/faded brownish wing (in which nothing replaced).

However, I'm now swinging back towards Taimyr Gull for it based on unpatterned greater coverts (throughout) and weak window on the inner primaries (though there are pale spots near the tips).

As there are a few other things wrong with it for Taimyr Gull, this is one that is not fitting conveniently into category. Any help with it or comments would be much appreciated!

Steve

lou salomon · Jan 15, 2018

i'd share exactly your thoughts on this bird: it appears to be a mongolicus on large size, tail pattern, early replaced scaps and wear but the unpatterned GC row appears to be unusual. not sure if the yellow bill base is a hint towards either. anyhow, my gut feeling says mongolian gull. cachinnans-like tertial pattern (moonlike crescents) is also sth. i've not yet seen in taimyrensis.

JANJ · Jan 15, 2018

Hi Steve!

Trouble, trouble! (?) On a first look at the time given, they surely look like mongolicus. However, there´s something not right, for instance, not only the greater covert pattern but also the inner primary pattern, which both would be better off on a taimyrensis, the only bad thing about taimyrensis is the advanced moult and wear!

Take a look at these mongolicus by Chris Gibbins from Korea at approx the same time of year, hope you can see these Steve:

https://www.facebook.com/profile.ph...67876138293.1073741831.100011452496541&type=3

I have attached two pic of a gull from inner Mongolia on the breeding location of mongolicus and this one looks like the one... but notice the inner primaries and greater coverts

JanJ

JanJ

SteveMM · Jan 16, 2018

lou salomon said:
i'd share exactly your thoughts on this bird: it appears to be a mongolicus on large size, tail pattern, early replaced scaps and wear but the unpatterned GC row appears to be unusual. not sure if the yellow bill base is a hint towards either. anyhow, my gut feeling says mongolian gull. cachinnans-like tertial pattern (moonlike crescents) is also sth. i've not yet seen in taimyrensis.

Thanks, Lou.

Yes, tail pattern is another thing that seems to better fit Mongolian. I also think wing shape is not like Taimyr Gull, either, with that very broad arm and short triangular hand.

I just don't know what should take precedence here - the greater covert/inner primary pattern (not Mongolian) or, quite literally, everything else (all Mongolian)!

Steve

SteveMM · Jan 16, 2018

JANJ said:
Hi Steve!

Trouble, trouble! (?) On a first look at the time given, they surely look like mongolicus. However, there´s something not right, for instance, not only the greater covert pattern but also the inner primary pattern, which both would be better off on a taimyrensis, the only bad thing about taimyrensis is the advanced moult and wear!

Take a look at these mongolicus by Chris Gibbins from Korea at approx the same time of year, hope you can see these Steve:

https://www.facebook.com/profile.ph...67876138293.1073741831.100011452496541&type=3

I have attached two pic of a gull from inner Mongolia on the breeding location of mongolicus and this one looks like the one... but notice the inner primaries and greater coverts

JanJ

JanJ

Thanks for the response, Jan. Not entirely sure from it which side of the fence it puts you on, though! Are you saying you favour Taimyr Gull?

Steve

SteveMM · Jan 16, 2018

Just for illustrative purposes (and to illustrate Jan's point)...

On Mongolian Gull, the pattern on the inner primaries is typically striking, with pale of the inner webs extending onto the outer webs, leaving isolated black 'arrowhead' markings at the tip. You can see this on the right-hand bird in the composite.

On Taimyr Gull, the outer webs are dark (somtimes with faint pale 'lozenges' in their centres distally), much as in the left-hand bird. The left-hand bird is, unfortunately, the 'problem' bird!

Should this (plus the dark greater coverts) carry more weight than structure, tail pattern, and (above all else) timing of moult when identifying this bird? This bird did arrive looking like this in early December!

Steve

JANJ · Jan 16, 2018

Sorry Steve, being over cautious. Your bird should be mongolicus. 😉 Good pic!

JanJ

SteveMM · Jan 17, 2018

JANJ said:
Sorry Steve, being over cautious. Your bird should be mongolicus. 😉 Good pic!

JanJ

Thanks again, Jan!

I could have easily been convinced either way with this bird, but with two votes in for Mongolian Gull I'll stick with that one I think!

Steve

First-winter Larus, Chiayi County, Taiwan: Mongolian or not? (1 Viewer)

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