Caspian Gull? from Denmark (1 Viewer)

At present we have a Caspian lookalike with a bit of argentatus-jizz in Aarhus Harbor. This is the third winter that we see this adult gull in the harbor and it is a completely match between years. All three years is has the white summer plumage head from November when arriving at our site.

It has only black on outer edge of p5, but also a little black spot on p4 (only on left wing), grey tongues on the five outer most primaries, all white tips to p10, darker upperparts than argentatus, when seen on water it gives a classic cachinnans jizz with slender elongated rear and flat back, but when seen standing on ground it gains some argentatus appearance due to head profile and body.

Is it a pure cachinnans or most likely a hybrid cachinnans x argentatus or just an aberrant argentatus in advanced moult?

November 2009:

http://2.bp.blogspot.com/_PYB8xNHlQmw/Syd9FXg3UsI/AAAAAAAAC9I/VvQl66GCDnU/s1600-h/cachcollage2.jpg

http://3.bp.blogspot.com/_PYB8xNHlQmw/Syd9FNihQ5I/AAAAAAAAC9A/zo-maXSIRLo/s1600-h/cachcollage1.jpg

http://3.bp.blogspot.com/_PYB8xNHlQmw/SyeB_O01ElI/AAAAAAAAC9Q/JegoTtbzzy8/s1600-h/cachcollage3.jpg

http://2.bp.blogspot.com/_PYB8xNHlQmw/SwW4gC3OJ1I/AAAAAAAACu8/Wfl9O2QA5p4/s1600/mågesp2-11-11-09.jpg

http://2.bp.blogspot.com/_PYB8xNHlQmw/SwW4gDN6S3I/AAAAAAAACu0/QarZWC2gcDs/s1600/mågesp1-12-11-09.jpg

http://3.bp.blogspot.com/_PYB8xNHlQmw/SwW4fzHge0I/AAAAAAAACus/SHlLqYMimYg/s1600/mågesp1-11-11-09.jpg

December 2007

http://2.bp.blogspot.com/_PYB8xNHlQmw/SPxbdtkt1iI/AAAAAAAACFU/_BWJ5-l4XDw/s1600-h/IMG_1685.jpg

http://1.bp.blogspot.com/_PYB8xNHlQmw/SPxbeDYmrdI/AAAAAAAACFc/hpCJzQwv4Og/s1600-h/IMG_1686.jpg

http://bp3.blogger.com/_PYB8xNHlQmw/R5PBm_HHXmI/AAAAAAAAAak/xEejUdks0I8/s1600-h/DSCN7023_red.jpg

November 2007:

http://bp2.blogger.com/_PYB8xNHlQmw/R5PBnvHHXpI/AAAAAAAAAa8/J7KknvwiYmU/s1600-h/DSCN6857_red.jpg

Obviously a tricky one this - over 100 views & no replies!!! The eye looks to dark compared to the Herrings around - is this right or just something that is showing in the photos?
The asymetrical P4 spot could have something to do with a dodgy parentage or grand-parentage even, I assume hybrids mate back with one of their parent species if they are fertile giving 2nd generation very confusing things.
Good luck with it.

Davo :h?:

I agree with you Kent that it doesn't look spot on for Caspian Gull and would also agree with yourself and Davo that there could be some influence from another species at work here.

Davo,

The eye is paler than in average cachinnans, but certainly within their variation and when seen at some distance it stood out as being rather dark in contrast to nearby argentatus. But we also see dark-eyed argentatus, thus the eye colour is only indicative at this stage as we have not yet seen the gull at such close range the we could determine whether colour of the iris peppering is just dark or green like a cachinnans

Thanks

it does look a lot like a caspian - knowing much of its variation range, but i can see where the unwell feeling comes from. none of the features that it shows are as itself exclusive of either weird (eastern?) argentatus or of cachinnans but with a strong emphasize on cachi - who knows how the 2-3 gen. backcrosses look (a few 2nd gen. are on the net).

A few suggestions here:

http://www.talk.gull-research.org/viewtopic.php?f=13&t=137

JanJ