Could this be an atlantis?

[Ruud Altenburg]

Magnus Robb photographed this rather dark mantled and dark hooded 3cy YLG at Berlenga, Portugal, last week. Obviously this is what one would expect an atlantis YLG to look like, but Magnus wondered if a hybrid YLG x LBBG could be excluded? My field experience with both atlantis and such hybrids in autumn is nill, but hopefully someone on this forum has.

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[adriaens]

Als ik me goed herinner (heb het nu even niet nagekeken) is die zwarte snavelbasis iets dat wel vrij vaak voorkomt bij 3w atlantis (en minder bij Geelpoot en KLM).

[JanJ]

Als ik me goed herinner (heb het nu even niet nagekeken) is die zwarte snavelbasis iets dat wel vrij vaak voorkomt bij 3w atlantis (en minder bij Geelpoot en KLM).

Which in other words means...

JanJ

[lou bertalan]

...that a black bill base is more commonly found in 3cy atlantis than in michahellis. well, at least we know that some 3cy nominate michs do have dark bills...

what about those legs - they don't look yellow to me.

lou

[Rui_Caratão]

3 days ago another atlantis type gull was found in Peniche harbour, only 6 NM from Berlenga where Magnus saw his gull, yesterday I managed to see the gull from Peniche. I am not quite sure what to think, though!!

Note the strong tasus, with heavy marked scales.
Pink legs on 3cy atlantis, October in Azores http://joshrjones.blogspot.pt/2011/10/azores-day-9.html

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[Rui_Caratão]

My gut feeling keeps saying.....LBBG

[adriaens]

No. This one (too) looks great for atlantis, I believe.

[Rui_Caratão]

No. This one (too) looks great for atlantis, I believe.

I guess so, everything seems to fit in, I must say that the grey tone was as expected paler than the graellsii present and darker than most YLG.
I would be happier if the bill was shorter and stronger, but even lusitanius from Berlengas/Peniche mostly females have thin bills and rounder heads.
My main doubt still is the same as Magnus, can LBBGxYLG be rulled out?

[adriaens]

I have some experience with hybrids of YLGull (see our recent paper in British Birds, September 2012), though not really in winter.
Anyhow, neither YLG nor LBBG show this type of head streaking. Especially the strongly streaked malar area looks very convincing.
Note also the staring, pale iris - even though the bird is not quite adult yet.

[JanJ]

Thats what I expect an atlantis to look like! However, given the variation in michshelliz one should perhaps not jump to
conclusion....

JanJ