Herring
Gull - Zilvermeeuw (argentatus & argenteus)
(last update: 07 april 2004)
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Herring Gull H-68803 9cy (argenteus), February 07 2003, Le Portel / Boulogne-sur-Mer, France (50.44N-01.34E).
A 9cy argenteus: Bruxelles H-68803. Ringed as pullus on July 12 1995 at Zeebrugge, Belgium (51.20N 03.11E). It has a complete white head, all winter streaking lacking by early February. Normally winter streaking in argenteus can be very obvious in early winter (November-December), either as bold clouded patches or as fine, delicate, demarcated streaks. However, adult argenteus already return to the colonies in January-February, maybe depending on the weather conditions (mild winters north to 53° latitude along the coast of the North Sea). It's unknown in what way and to what extend weather conditions influence body feather moult, but from January onwards, adults may appear with snow-white heads. By the second week of February, at least 25% of adult argenteus from the Netherlands are in active moult on the head. This is often obvious in the feathers around the eye, which are shed by the second week of February, leaving a naked ring around the eye (visible at close range).
The primary pattern of
this adult argenteus matches ordinary argenteus: The white
mirror on P10 is almost completely divided from the white tip by a sub-terminal band.
The sub-terminal band is broken at the very centre. The medial band
continues over quite a large range on the inner-web of the P10 primary. The mirror on P9 is concentrated at the inner-web, just
not reaching to the feather edge at the outer-web. This bird, as many argenteus,
shows much black in
the outer-wing. P6 has a broad sub-terminal band and the sub-terminal band
on P5 is broken, leaving two triangular spots on the edge of both inner
and outer-web. Adult
Herring Gull with so much black in the outer-wing are typical
representatives of the taxon argenteus.
Note the relatively dark orange orbital ring.
Note also the following characteristics for argenteus:
- It is pale grey on the upper-parts, matching British argenteus. Argenteus from the UK, France, Belgium and the Netherlands are slightly paler grey than argentatus from northern Norway.
- The black patch between the grey centre and the white mirror, the "medial band", is very broad on primary P10. This medial band extends over quite a range on the inner-web, a feature commonly found in western argenteus. As the table below shows, northern argentatus may have the medial band very limited along the inner-web of P10 and in some northern birds, this medial band doesn't reach the inner-web at all, creating a thayeri pattern on P10. Such a P10 thayeri pattern is very obvious in some of the images in the adult HG January Section. A thayeri pattern can be obvious on P9 and this feature too was investigated by Barth, as the second column in the table shows. Such a thayeri pattern can be found more commonly in northern argentatus populations.
- A complete sub-terminal band on P10 is found in only 15% of argentatus. Adult argenteus normally shows a complete black sub-terminal band or reduced sub-terminal black at the edge of the inner-web and outer-web (broken sub-terminal band at the centre). Only a small minority of western argenteus completely lacks any sub-terminal markings. Extensive research on the P10 pattern of Scandinavian argentatus was done for Norwegian birds by the Norwegian ornithologist Edvard Barth, and is presented in the table below:
| 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 spotting 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 |
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