Herring Gull - Zilvermeeuw (argentatus & argenteus)

(last update: 29 maart 2004)

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(4 images) Herring Gull C798 8cy (argentatus), July 11-15 2003, Tampere, Finland (61.31N, 23.43E).

8cy argentatus yellow C798, ringed as pullus on June 30 1996 in Hauho, Finland (61.22N 24.55E). From 1999 onwards, there are about 100 observations, all from Tampere dump. In many respects a classical full adult nominate argentatus, with a yellow hue on the pink legs, clear yellow iris, red orbital ring and red gonydeal spot confined to the lower mandible. C798 has an obvious sharply-demarcated sub-terminal black spot on the outer-web of P5. On P10 the white mirror is well separated from the greyish inner-web by a black medial band, reaching to the inner-web's edge. The complete moult has started, with P1-P3 replaced and P5-P10 still old. This moult score corresponds with the typical moult score in the wing-coverts: the outer median coverts are replaced and the central medians are still old.

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".