Herring
Gull - Zilvermeeuw (argentatus & argenteus)
(last update: 31 maart 2004)
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3x Herring Gull adult (argentatus), July 11-15 2003, Tampere, Finland (61.31N, 23.43E).
Top image: Adult argentatus in active moult at Tampere, with the primary moult started.
P4-P10
still old and P2 fully grown. PMS = 10.
Pattern on outer primaries: 7III. Complete band on P10 and P9. Black
triangle on outer-web of P5. Division between grey and black unknown.
Image below: Adult argentatus in active moult. P7-P10
still old, P4 fully grown; primary moult stage (PMS) = 24.
Pattern on outer primaries: 7VA. Complete band on P10 and P9. P5 growing
and complete band just visible. Sharp division between grey and black on P10.
Figure right: Wing-tip pattern in adult Herring Gull argentatus / argenteus.
| 1 | Thayeri
pattern on P9 and/or P10. |
| 2 | White
tips on P9 and P10. |
| 3 | White
tip on P10, black triangles on P9, mirror P9 on both webs. |
| 4 | Black
triangles on P9 and P10. |
| 5 | White
tip on P10, full band on P9, mirror P9 on both webs. |
| 6 | Black
triangles on P10, full band on P9. |
| 7 | Full
bands on P9 and P10, mirror P9 on both webs. |
| 8 | Black
triangles on P10, mirror P9 only on inner-web. |
| 9 | Incomplete
band on P10, mirror P9 only on inner-web. |
| 10 | Full
band on P10, mirror P9 only on inner-web. |
| 11 | Incomplete
band on P10, no mirror on P9. |
| 12 | Complete band on P10, no mirror on P9. |
Score of P5:
| I | No
black on P5 (e.g. fig 1 & 2). |
| II | Diffuse
black on outer-web of P5 (e.g. fig 3). |
| III | Sharp
triangle on outer-web of P5 (e.g. fig 4 & 7-12). |
| IV | Sharp
triangle on outer-web, diffuse line on inner-web (e.g. fig 5). |
| V | Complete
band on P5 (e.g. fig 6). |
Score of division line between grey centre and black medial band:
| A | Sharp
division between grey and black. |
| B | Diffuse
division between grey and black. |
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".
Bottom image: Another adult argentatus,
also in active moult at Tampere, with the primary moult in progress.
Probably a female. P7-P10
still old, P4 fully grown; primary moult stage (PMS) = 23.
Pattern on outer primaries: 1A. Thayeri pattern on P9 and sharp division between grey and black on P10
(code A). P5 hard to judge.