'Apparent' Caspian gull, at Nagasaki

Aug. 2008 K Kagoshima

1.外観と状況：Whole appearance and circumstance　

This bird had been seen during Dec. 12 2004 at Nagasaki New Fishing Port(Japan). It looked very slimer than any others. Structure, such as neck, wings and legs were longer. Legs were pale pink with blueish tinged.
Checking other points, I suspected this gull would be a Caspian gull L.cachinnans

A 'taimyrensis' was behind this gull and most of others were Vega gull.
As for this port, 200-1000 large gulls always winter, most of them are Vega, Staty-backed, and rarely Mongolian gull.

2.頭部：Bill & hindneck

Bill was greenish with black marks on both mandibles. Fine streaks were restricted on neck.. Small 'beady' dark eyes were impressible.

3. 翼のパターン：wing pattern

Primary moult had already completed. No subterminal band between tip and mirror. Primary and wing projection were longer than usual Vega gull.

On Dec.30 2004 this bird came back to me.
This P10 'tongue' which is running up the black part of inner-web was distinctively long. Greater undercoverts looked comlpetely white. These points seemed to separate this bird from usual Mongolian gull 'mongolicus', according to 'Yesou 2001', and also usual Vega gull. P10 to P5 had black parts.

５.考察と結論：Discusion and Conclution

Nowadays, It has been said that Caspian gull Larus cachinnans consists of 2 sub species, cachinnans and mongolicus. Spp. cachinnansare is increasing in western Asia (Larson 1998).

As for this indivisual, appearrance and wing-patterns indicate that this bird seems to be close to Caspian gull(L.c.cachinnans) rather than spp.mongolicus.
But I didn't remember if this would have behaved 'Albatross posture'. Some point didn't perfectly fited to Caspian, as somewhat pinkish legs, not so pararell bills and slightly paler eyes.....In Eastern Asia, situation around hybrid gulls are very complicated, especially such a smaller size of gulls.

As Japan is far from breeding site of cachinnans, this gull also might have been a hybrid between the said two taxa, which might have bred at Mongolia or somewhere central Asia

Reference:
Jonson, L. 1998 Yellow legged gulls and yellow legged Herring Gull in Baltic. Alula 3，
「Yellow-legged gulls and yellow-legged Herring Gull in the Baltic」
Klaus Malling Olsen and Hans Larsson, 「Gulls of Europe,Asia and North America」CHRISTOPHER HELM LONDON 2003
Yesou P. (2001) Phenotype variation and systematics of Mongolian Gull. Dutch Birding 23:65-82

Above: L.c.mongolicus at Nagasaki( other page in detail)

Above: L.vegae at Choshi

６．日本語要約（長崎弁）：Abstruct by Japanese(Nagasaki dialect)

ようわからんカモメ類が長崎新漁港に来るとよね。これはうんと西の方に生息するCaspian　gull Larus cachinnans cachinnansごたる特徴を持っとうと。特に翼のパターンはよく似とっと。ばってん、繁殖地からよう離れとるけん、おいは、モンゴルカモメMongolian gull L.c.mongolicusとの交雑種かもしれん、思うとるとですよ。こいたちは、まれにおっとです。

P10 'tongue' was broader, longer, and whiter than usual Mongolian gull and longer than Vega gull.