Iceland, Glaucous and Caspian Gulls - interesting feathers

Gulls have never been in the Dutch spotlights as they are right now. Since the influx of Iceland Gulls in Western Europe and the appereance of a possible American Herring (smithsonianus) in our country, Gullfeathers are hot!

Yesterday, Theo and I went to Den Oever, Noord-Holland to visit the candidate third-winter smithsonianus that is present for more than a week now. In this topic the bird is still in debate, but the opinions are a bit turned to the side of: close, but no sigar. Peter Adriaens has been studying a while on this taxon, and made clear that there are some  points against a good smithsonianus:

a. It does have 'straight, horizontal upper borders to the black pattern on both P6 and P7' (citation).
b. It doesn't have solid, black or darkbrown markings in the secondaries or adult-type secondaries.

Only the left wing is adult-type and could be used to interpret the pattern. (Albert de Jong)

In the field, the bird looked rather small. Is it still in the range of third winter smithsonianus or just an argentatus with a pattern we rarely see? If you like to read more about this interesting topic, note these pages on the ORG-site. Or have a look at these pictures.

Also, this giant white one was present in the same harbour.  The ID of this bird is without any doubt a second-winter hyperboreus. I think the Latin name tells something about the bird?

Larus hyperboreus - Glaucous Gull, 2w male (Albert de Jong)

After Den Oever, we visited the harbor Urk to look for the reported adult Glaucous Gull and the second winter Iceland Gull. Only the latter we found, and also four Caspian Gulls (two 1w, one 2w, one ad) and a Yellow-legged Gull. 

Cachinnans and argentatus

Larus cachinnans - Caspian Gull - adult

Larus cachinnans - Caspian Gull -2cy

The Iceland Gull shows brown shadings in the outer primaries. More birds with shadings (but without a dark hockeystick pattern towards the tips and a ghostmirror in p10) in the primaries have been reported and are presumed dark glaucoides rather than pale kumlieni. More about this interesting topic could be found here and on the blog of Chris Gibbins.