Larus fuscus intermedius ? - Sesimbra (Portugal) (1 Viewer)

[Luís Vieira]

Hi everyone,

I was looking back at some photos that I took on January 2nd 2022 with my cell phone in Sesimbra, a small town on the west coast of Portugal, south of Lisbon. I assume that the gull with the darker back is Larus fuscus, and appears to have characteristics of Larus fuscus intermedius. I add for comparison a photo of a (likely) L. michahellis gull taken at the same time in the same exact location. None of the photos were treated in any way. Unfortunately the photo of the putative L. fuscus gull is the only one I got. Would you please give me your expert opinion on the gull with the darker back?

Thanks a lot.

Luís

 

[Alexander Stöhr]

Hello,
I agree with you: left bird is an adult LBBG "with characteristics of Larus fuscus intermedius." "Darkness value of the mantle is on the darker end of variation of this ssp, but easy within variation.
Please compare to this LBBG with an even blacker mantle (and old, worn primaries, but also sadly a poor condition) ( 31.10.2018, Prenzlau, NE-Germany, discovered by Heino Hauf. Thanks!)

https://flic.kr/p/2ndt1wQ

Regarding mantle colour of different ssp, please read the excellent papers from Andreas Noeske:

https://club300.de/publications/013_lbb_gulls/Noeske_Mantelfaerbung_der_Heringsmoewen.pdf

Club300 Germany

and here another excellent one from Peter Adriaens : You are being redirected...


The right bird is harder, at least for me. With such a dark mantle, why not another LBBG?
My thoughts:

• yes, unstreaked head is not good for a LBBG in January
• but where is the red gape of many YLG?
• darkness value of grey hues are easy changed by camera settings (no offense, its the software that makes this) and you have seen this bird in the field. Human eyes and the brain are far more effective in judging the mantle shade in the field.
• but when the picture (and my screen) represents the real mantle tone (including lacking even the slightest blueish hue), your bird would stand out as a darker mantled bird among adult YLG in SW-Germany.
• Please compare to this dark mantled YLG (enhanced by low, flat evening/moring light?) here: Gull Research Organisation

Conclusion? I hope for more pictures and comments for the second bird. Thank you!

 

[Luís Vieira]

Hi Alexander,

Thanks a lot for your comprehensive comments and the literature suggestions. I will certainly look at these closely!

As you said, the human eyes are far better in judging the true mantle color of gulls. From my perspective (i.e., "eyes"), the gull in the right was a YLG with a slightly more darker grey back than usual (just as in the photo from the Gull Research Organization that you mentioned). In this new photo, the mantle color looks a little bit less dark than in the previous photo. Do you think now this favors the YLG "hypothesis"?

Thank you. Best regards.