CGs, HGs or Hybrids??

[Ronald Klein]

Thayeri-pattern is quite common in Caspian Gulls. The iris can be paler, but this is in the most cases not similar to the "snake-eyes" of the most adult Herrings.

[marsmuusse]

Hi Gabor,
Very nice pictures! The adult should be cachinnans indeed, both 2nd winter birds look like michahellis I think; very extensive partial autumn moult, inner greater coverts either already grey or grey-based with brown anchor.
Argentatus from Norway and N Russia do not show such extensive moult normally, and if you think of argentatus which may cause trouble, it will be birds from Poland / Finland / Baltic that have to be ruled out. This can be notoriously difficult, as some Baltic argentatus show extensive partial autumn moult as well. In fact, 2cy argentatus in complete moult in summer in SW Finalnd (Tampere) are slightly ahead when compared to Larus argentatus s.l. (argenteus & tatus) at my local patch, Scheveningen harbour, Holland. Not only that, in moult they are also ahead of summer Herring Gulls at Boulogne-sur-Mer, NW France! So it is no real surprise that the partial autumn moult may be quite advanced in birds from Finland in 2nd winter. Still, the pictures you have added recall michahellis rather than argentatus for me.
Some 2nd winter argentatus:

1. January 2004 Poland; bird from Finland:


2. January 2004 Poland; bird from Finland:


3. January 2007 Finland, unringed 2nd winter Herring Gull (ID Visa):


4.October 2006 Finland; bird from Finland:


3. January 2004 Poland; bird from Russia:

[hieraaetus]

[quote="marsmuusse"]Hi Gabor,
Very nice pictures! The adult should be cachinnans indeed, both 2nd winter birds look like michahellis I think; very extensive partial autumn moult, inner greater coverts either already grey or grey-based with brown anchor.
Argentatus from Norway and N Russia do not show such extensive moult normally, and if you think of argentatus which may cause trouble, it will be birds from Poland / Finland / Baltic that have to be ruled out. This can be notoriously difficult, as some Baltic argentatus show extensive partial autumn moult as well. In fact, 2cy argentatus in complete moult in summer in SW Finalnd (Tampere) are slightly ahead when compared to Larus argentatus s.l. (argenteus & tatus) at my local patch, Scheveningen harbour, Holland. Not only that, in moult they are also ahead of summer Herring Gulls at Boulogne-sur-Mer, NW France! So it is no real surprise that the partial autumn moult may be quite advanced in birds from Finland in 2nd winter. Still, the pictures you have added recall michahellis rather than argentatus for me.
Some 2nd winter argentatus:
[quote="marsmuusse"]

Hi Mars,

Thanks a lot for sharing your opinion!
I will be honest with you, YLG never came to my mind as a possible explanation:) The shade of the mantle was just so pale compared to the other birds that they kind of stuck out of the crowd.

I attached some pictures; one from Dec. 2012 and another one from last year to show what I expect to be a "normal" YLG:) and also a 2nd-winter HG from the last week.

Thanks again!
It's always good to hear thoughts of the more experienced.

Cheers,

Gabor

[adriaens]

Hi Mars (and others),

the first bird shows a lot of brown marbling on the inner primaries (download/file.php?id=3603),
which is not shown by 2w Yellow-legged Gull. The tail pattern also looks wrong to me.

The second bird has a rather long and rectangular pale tongue on P10 (download/file.php?id=3601),
which is not usually this extensive in 2w Yellow-legged Gull, particularly not when the underwing-coverts are so brown.

Both birds look like Herring Gulls to me.