Hybrid or pure?

[Ruud Altenburg]

This is an old one from Amsterdam, 24-12-10. Can this still be classified under variation within Herring or should I think of influence of Caspian?

[JanJ]

Hi Ruud.

That might seem a good question. Structurally it fits Herring very well. On the other hand, structure might be difficult to judge properly - partly for the reason that it might after all be a hybrid?
However, I don´t see anything - perhaps apart from the rather unmarked breast and upper belly, which in it´s self doesn´t exclude a Herring, that points away from a pure Herring. How about the scapular pattern then? Anything there that might suggest Caspian influence. Seems to be within the variation of Herring imo.
Not so dissimilar to this argenteus in fact, give and take a few detailes. But then again I might be wrong

http://www.gull-research.org/hg/hg1cy/5 ... ladec.html

JanJ

[Ruud Altenburg]

Hallo Jan

thanks for your reply. Surely it's closest to Herring, structurally especially. It just shows an unusual combination of tertial and greater covert pattern, which, in this combination, resembles Caspian. It's also rather long-winged compared to our local birds but this could well be a wintering argentatus.

Cheers

Ruud

[JanJ]

Just to show one example of a 2cy argentatus Herring - which it is of course ( ) taken by Alan Dalton Stockholm 28.2.2011

JanJ