(4 images) Herring Gull 2cy (argentatus), November 22 2001, Westkapelle, the Netherlands (51.33N-03.25E). All picture by Pim Wolf.

• The extensive clouded brown mottling on the head and the under-parts,
• The almost complete black tail,
• The pale rump, with only thin barring at the upper-tail coverts,
• The relatively dense streaking on the under-tail coverts,
• The variegated pattern at the greater coverts,
• Rather intense pink-coloured legs,
• Slightly washed-out pale brown window in the inner primaries, resulting in a less pronounced pale window compared to European Herrings.

On the other hand, some features advocate the North European nominate race argentatus (many thanks to Peter Adriaens and Martin Reid):

• The dark iris,
• The relatively dark bill, lacking a distinct paler base,
• The pattern on under-tail and upper-tail coverts fall within the variation known for European Herring Gulls. Here, the upper-tail coverts show fine dense barring with the white base broader than the dark pattern. In smithsonianus, the pattern would be reverse: barring would be broader than the pale base, resulting in an overall dark brown or greyish feather group. Under-tail coverts in smithsonianus are darker and especially the base of the under-tail coverts have to be barred as well. Here, barring is concentrated on the outer half of the feathers, the base is rather pale, hardly patterned. Nevertheless, note the dark barred under-tail coverts viewed from left, together with the plain dark under-parts and the plain brown hind-neck,
• The same applies for the dark under-parts, still falling within the variation of European Herrings. Smithsonianus often shows "clouded or mottled patches" on the under-parts, more uniform than the broad bars in this individual,
• Pattern on the tertials is vermiculated at the fringe and the pale tips are relatively broad in the older feathers. At the tip of tertial #4, some internal paler patterns are visible. Also, the moulted new upper tertials should be darker in smithsonianus,
• Structurally, the jizz of this individual is probably more in line with European birds, with the rounded head (which should be more angular in smithsonianus) and the short bill with obvious gonydeal angle (longer and surprising parallel in smithsonianus).

To compare this individual with other November and December 2cy birds, some links of smithsonianus on the web are worth visiting:

Martin Reid:
http://www.martinreid.com/hsmitp10.htm (early December)
http://www.martinreid.com/hsmitp27.html (late November)
http://www.martinreid.com/hsmitp35.html (late February)
http://www.martinreid.com/hsmitp41.html (March & December)

Steve Hampton:
http://www.geocities.com/RainForest/Canopy/6181/smith1.htm (three second winters from December 22)

Osao Ujihara:
http://isweb15.infoseek.co.jp/animal/larus/smith2w001216/smith2w001216.html (a second winter from Japan, at December 16)

Dick Newell:
http://magikcircle.com/birds/image.asp?title_id=179&group_id=174

Frode Falkenberg:
http://www.zoo.uib.no/~falken/gull/ufo_argsm03.php3 (another problematic second winter bird from January)

Smithsonianus Herring Gull has never been recorded in the Netherlands. Rik Winters added: "Herring Gulls with (almost completely) black tail are not common, but can be found daily in the Netherlands and probably originate from northern populations". Thanks to all who sent information. All comments were much appreciated.
Pim Wolf or Mars Muusse