Herring
Gull - Zilvermeeuw (argentatus & argenteus)
(last update: 08 december 2003)
Home
Links
to Gull Sites
Gull Taxa
Gull Topography
Grey & Colour Charts
Locations in NW Europe
Summaries of Articles
About ORG
@
Herring Gull adult (argenteus), March 17 2003, Le Portel / Boulogne-sur-Mer, France (50.44N-01.34E).
Two adult argenteus,
photographed and probably breeding in the harbours of Boulogne-sur-Mer.
Preliminary data of several French metal-ringed argenteus reveal
that these local breeding argenteus from the Calais region are
slightly different from British, Belgian and Dutch argenteus:
- they develop clear snow-white heads early in the season, hence the moult
cycle is advanced compared to argenteus from northern populations
(as is easily explained by their hormonal cycle; breeding at a southern
latitude than other argenteus and argentatus populations,
adults have to prepare earlier for breeding conditions)
- the wing-tip pattern is similar to the pattern found in western argenteus
populations: P10 often with a complete black sub-terminal band, small
mirror on P9 and the medial band of P10 extending over a vast range along
the inner-web of P10
- the legs often show a yellowish hue on the pink, especially early in the
breeding season. This is sometimes seen in Dutch argenteus as well,
but not as often as in these birds from the Calais region
- the orbital ring is often orange-red to coral-red, not the typical
yellow or yellow-orange color of northern argenteus
- early spring (January - May) the gonydeal red spot may extend
obviously on the upper mandible, a feature hardly found in northern argenteus
populations
- some adults from the Calais region may appear relatively dark grey
Summarizing these points, argenteus from the Calais region show features related to michahellis more often than argenteus from northern populations (Belgian and Dutch coast, the U.K.).
The primary pattern of these adult argenteus matches ordinary argenteus: The white mirror on P10 is completely divided from the white tip by a sub-terminal band in the front bird. 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 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 confined to the edge of the outer-web. Adult Herring Gull with so much black in the outer-wing are typical representatives of the taxon argenteus. Note the red-orange orbital ring in both birds.
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. 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 |
||||||||||||||||||