Herring
Gull - Zilvermeeuw (argentatus & argenteus)
(last update: 30 maart 2004)
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(3 images) Herring Gull C240 7cy (argentatus), July 16 2003, Tampere, Finland (61.31N, 23.43E).
7cy argentatus black C240, ringed as pullus on July 02 1997 in Pälkän, Finland (61.35N 24.12E). From year 2000 onwards, there are about 70 observations, all from Tampere dump, except one: a winter observation as 4cy, February 03 2000 from Gdansk, Poland (54.33N 18.55E). In many respects a classical full adult nominate argentatus, with a yellow hue on the pink legs, white-yellow iris, orange-red orbital ring and red gonydeal spot confined to the lower mandible. The white mirror on P9 and P10 is hardly separated from the greyish inner-web by a black medial band, not reaching to the inner-web's edge on P9, hence creating a so-called thayeri pattern. The complete moult has started, with P1-P3 replaced and P6-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 median and lower lesser coverts are now 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.
Argenteus 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".
