Herring Gull - Zilvermeeuw (argentatus & argenteus)

(last update: 30 maart 2004)

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(5 images) Herring Gull CV106 6cy (argentatus), July 15-16 2003, Tampere, Finland (61.31N, 23.43E).

6cy argentatus white CV106, ringed as pullus on June 28 1998 in Pälkän, Finland (61.30N 24.13E). From 2001 onwards, there are about 35 observations, all from Tampere dump. 
A (young) adult nominate argentatus, with old 5th generation outer primaries, high primary moult score (PMS), pink legs, yellow iris, red orbital ring and red gonydeal spot confined to the lower mandible. This young adult has more black in the outer-wing than usual, with a complete sub-terminal band on P10 and a small mirror on the inner-web of P9. P5 has a complete sub-terminal band as well. The white mirror on P10 is separated from the greyish inner-web by a broad black medial band. High PMS: 23. P7-P10 old, P5 growing.

From June to December, adult argentatus undergo a complete moult resulting in so-called "winter plumage". By August, the first neat streaks can be found on the crown and hind-neck. After the complete moult is finished by late autumn, the head will often show extensive 'winter streaking'. 
From June onwards, the new plain grey wing-coverts are moulted in, starting with the outermost median coverts and ending in the carpal edge. By the end of the complete moult, when P10 is completely replaced (sometimes as late as mid-January in argentatus), the scapulars, mantle, all the wing-coverts, rectrices and remiges will be replaced as well.

During the summer, the primaries are moulted. In adult argentatus, the last outer primary P10 will be fully grown by January in the most northern population, by early December in southern populations, about equal to West-European argenteus.

Adult northern argentatus show a different pattern in the outer primaries, compared to argenteus. In argentatus, especially from northern Scandinavia, the black markings on P5 are limited or absent and, if black on P5 is present, this black has diffuse edges. Most often, these black sub-terminal markings are completely lacking on P5. In Baltic argentatus, black on P5 is normally confined to the outer-web, with sharply defined edges.
normally has a black sub-terminal band on the top of P10, dividing the tip from the mirror. If the black sub-terminal band on P10 is broken, the outer-web of P10 still shows black marking. Argentatus normally completely lacks sub-terminal markings, also on the outer-web of P10. Some argentatus completely lack black along the edge of the inner-web, creating a so-called "thayeri pattern".