Fuscus Intermedius? (1 Viewer)

[martyrynin]

Hey,

I noticed this darker gull with the naked eye - Belfast, Ireland.

I wondered if it might be Intermedius? Also had more vibrant leg colour. Maybe it's just a different age/sex, although the other graellsii present matched the mantle colour of the bird on the left.

The difference is subtle, so may be nothing to talk abouf here, but as I said it did catch my eye.

I also thought the body shape to be more slender and slightly smaller.

 

[martyrynin]

I had a look at the difference of RGB values across various images of different exposure.
It was consistently between 1.5 - 2 kodak greyscale levels.

So I think the breakdown would be:

8 + 10: Both Graellsii
9 + 11: One Intermedius
10 + 12: One Intermedius

I also stumbled on this:

Lesser Black-backed Gull - BirdForum Opus

www.birdforum.net

I didn't know about opus - really good resource!

It mentions that Graellsii is larger and shorter winged, which I think I can see here, so it seems like there's a reasonable chance it could be.

 

[Alexander Stöhr]

Hello Leif,

do you know this interesting article from Andreas Noeske in German?

Club300 Germany

Loading...

www.club300.de

Your Gull would be at the darkest end of variation among Lesser Black backed Gulls in Germany. Even darker than this (Prenzlau, NE-Germany, 14.10.2018)

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

Or the attached LBBG, a quite regular dark LBBG (Schwetzinger Wiesen, SW-Germany, 16.06.2013).

So I think your Gull is indeed a good intermedius (/fuscus?) candidate, but I think its hard/nearly impossible? to get one step up to a confident intermedius/fuscus.
I think this is also the opinion of literature/experts.

Conclusion? I am sure, I just expressed your opinion in other words. But I hope my comment is helpful anyway.

 

[martyrynin]

Hello Leif,

do you know this interesting article from Andreas Noeske in German?

Club300 Germany

Loading...

www.club300.de

Your Gull would be at the darkest end of variation among Lesser Black backed Gulls in Germany. Even darker than this (Prenzlau, NE-Germany, 14.10.2018)

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

Or the attached LBBG, a quite regular dark LBBG (Schwetzinger Wiesen, SW-Germany, 16.06.2013).

So I think your Gull is indeed a good intermedius (/fuscus?) candidate, but I think its hard/nearly impossible? to get one step up to a confident intermedius/fuscus.
I think this is also the opinion of literature/experts.

Conclusion? I am sure, I just expressed your opinion in other words. But I hope my comment is helpful anyway.

Hey Alexander,

I'll definitely read through that paper at some stage - it looks good!

Yes it was my opinion that it's not possible to be sure, I was just curious what people might have thought.
There's also Dutch intergrades which would make it near impossible surely.

Worth noting this was in the evening, so the gulls will naturally appear darker of course, which is why I tried to focus on the difference between the two gulls.
If anything weaker light conditions would reduce the visible difference in mantle colour, but the black primaries offer a good base-line as well.