Viking Gull?

[JanBaert]

Hi everyone,

I'd like to get some opinions on this bird (seen on a roost in Belgium this evening, hence the poor quality of the pics). As I'm very unexperienced with Viking Gulls it's hard for me to evaluate potential overlap with leucistic Herring Gulls.






kind regards,

Jan

[Theo Muusse]

It looks like a herring to me, given the pattern of black on the outer primaries.
Difficult to see, looks wrong for Kumliens?

Theo

[marsmuusse]

Hi Jan,
From these images its hard to start any discussion I'm afraid. Have you made a sketch / drawing from the primaries, or can you tell a little bit more about the patterns?

[JanBaert]

Hi Mars and Theo,

I haven't made a sketch yet, but based on my field notes I'll try to make one tonight.
Short description:
- P10: black markings on both inner and outer vane. Marking on outer vane is only 1/5 of the total length, the marking on the inner vane doesn't reach the edge of the feather. The mirror merdges with the tip and there are no black markings (partially) separing both.
-P9: very little black markings restricted to the outer vane.
-P8&P7: complete bar near the tip, black markings reaching up the outer vane
- P6: might show a very small 'ghost like' bar but very hard to judge due to poor light conditions

- Quite right, P.A. noted a totaly white greater covert on the right wing, so this might indicate that some leucism is involved

Regarding potential confusion with Kumliens Gull. I think this option can be safely ruled out based on the pattern on P10&P9 (apart from it's size and structure). For a Kumliens showing well developed markings on P8&7 I wouldn't expect P9 to be nearly deprived of markings.

kind regards,

Jan

[N.J.G.]

A bird like that was often coming to sleep at Callemoeie, Nazareth during last weeks.
Mine has also black restricted to 4 primaries. However the mantle color is rather dark and profile doesn't make me think of Glacous gull. I consider mine as a nothern argentatus as can be seen on picture 369 of "gulls".