Herring Gull - Zilvermeeuw (argentatus & argenteus)

(last update: 31 maart 2004)

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3x Herring Gull adult (argentatus), July 11 2003, Tampere, Finland (61.31N, 23.43E).

Top image: Adult argentatus in active moult at Tampere, with the primary moult just started. P3-P10 still old and P1 & P2 missing. PMS = 2.
Pattern on outer primaries: 7IV. Complete band on P10 and P9. Diffuse broken band on P5. Probably sharp division between grey and black on P10.
Image below: Adult argentatus in active moult. P7-P10 still old, P3 fully grown; primary moult stage (PMS) = 21.
Pattern on outer primaries: 5 No black on P10, P9 mirror on both webs. P5 shed and division between grey and black on P10 hard to judge.

Figure right: Wing-tip pattern in adult Herring Gull argentatus / argenteus.

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:

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".

Two bottom images: Another adult argentatus, also in active moult at Tampere, with the primary moult in progress. P4-P10 still old, P1 fully grown; primary moult stage (PMS) = 8.
Pattern on outer primaries: 1IA. Thayeri pattern on P9 and sharp division between grey and black on P10 (code A). P5 without black sub-terminal band.

 

Table 4 from E.K. Barth, The circumpolar systematics of Larus argentatus and Larus fuscus with special reference to the Norwegian populations, 1968. 200 Norwegian birds. (Notation converted to what we use in the texts, MM).
locality sample size tip pattern P10 tip pattern P9 colour of P10 inner-web black present from P10 to:
1 2 3 4 1 2 3 4 5 1 2 3 5 6 P7 P6 P5 P4
East Finnmark 15 n 10 1 2 2 5 4 1 1 4 5 7 3 12 3 - 10 5 -
% 67 7 13 13 33 27 7 7 27 33 47 20 80 20 - 67 33 -
Tamsöy in Central Finnmark 33 n 17 7 6 3 10 10 6 0 7 12 20 1 23 10 - 19 13 1
% 52 21 18 9 30 30 18 - 21 36 61 3 70 30 - 58 39 -
Troms 29 n 17 8 3 1 11 9 4 1 4 3 20 6 24 5 - 24 5 -
% 59 28 10 3 38 31 14 3 14 10 69 21 83 17 - 83 17 -
Bodö and Röst 32 n 15 10 3 2 19 3 5 0 3 3 24 5 27 5 1 18 13 -
% 50 33 10 7 63 10 17 - 10 9 75 16 84 16 3 56 41 -
Tarva 20 n 8 7 3 2 11 5 4 0 0 10 8 2 12 8 1 7 10 2
% 40 35 15 10 55 25 20 - - 50 40 10 60 40 5 35 50 10
Stavanger and Lindesnes 42 n 18 13 4 6 23 12 3 2 2 15 23 4 37 5 - 13 29 -
% 44 32 10 14 55 28 7 5 5 36 55 9 88 12 - 31 69 -
Oslo Fiord 29 n 19 6 3 1 20 1 4 1 2 12 14 3 24 5 - 17 12 -
% 66 21 10 3 71 4 14 4 7 42 48 10 83 17 - 59 41 -
.
.
. .
1: all white
2: trace of black near tip
3: incomplete black bar near tip
4: complete black bar or black tip
1: broad white band over both webs
2: white spot on both webs
3: white spot on inner web only
4: no white spot present
5: 'thayeri-pattern'
1: like mantle colour
2: slightly lighter than mantle colour
3: markedly lighter than mantle colour
5: relatively sharp border between black and grey
6: gradual transition from black to grey
.