Herring
Gull - Zilvermeeuw (argentatus & argenteus)
(last update: 23 september 2004)
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Herring Gull 5.369.341adult (argenteus), September 19 2008, IJmuiden, the Netherlands (52.27N 04.33E).
A bird ringed Arnhem 5.369.341; ringed 08 July 2003 as 4cy bird when taken into care. So, this bird would now be in 9cy. Primary moult is in progress with P6 fully grown; P10 still old.
From June (often mid-May in France, Belgium and the Netherlands) to October, a complete moult will bring birds in so-called "adult winter" plumage. A new set of primaries will grow during the summer months and by September, the outermost primaries P9-P10 are still present in argenteus in the Netherlands and northern France. In most adults, the new primary P6 is just visible beneath the tertials and shows a clear sub-terminal band. At the same time, the median coverts, outer lower lesser and outer greater coverts have been renewed and strongly contrast with the old, abraded adjacent wing-coverts. In summer, the head is still largely white, but by September, most adults develop extensive 'winter streaking', in sub-adults strongly mottled brown contrasting with the white breast as in an executioner's hood. The scapular coverts are plain grey, lacking white crescents. The tertials show obvious white tips. The iris is yellow. The bill is yellow with a red gonydeal spot confined to the lower mandible. The orbital ring is yellow-orange or orange-red in argenteus. The legs are flesh-pink in Dutch argenteus, although the odd individual shows slightly yellowish legs.
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September primary moult scores in adult Herring Gulls at Scheveningen. |
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| . | 01.09.2000 | 05.09.2001 | 07.09.2000 | 18.09.2000 | 21.09.2000 | 21.09.2001 | 26.09.2001 | 30.09.2000 |
| 0 | . | . | . | . | . | . | . | . |
| 1 | . | 3 | 3 | . | . | . | . | . |
| 2 | 9 | 19 | 15 | . | . | . | . | . |
| 3 | 41 | 32 | 30 | . | . | . | . | . |
| 4 | 10 | 4 | . | 7 | . | . | . | . |
| 5 | 1 | . | . | 35 | 42 | 7 | 24 | 2 |
| 6 | . | . | . | 36 | 60 | 24 | 62 | 38 |
| 7 | . | . | . | 11 | 20 | 9 | 12 | 43 |
| 8 | . | . | . | 2 | 3 | . | . | 1 |
| n: | 61 | 58 | 48 | 91 | 125 | 40 | 98 | 84 |
| average | 3,05 | 2,64 | 2,56 | 5,63 | 5,87 | 6,05 | 5,88 | 6,51 |
| Variance (s2) | 0,38 | 0,48 | 0,38 | 0,77 | 0,58 | 0,41 | 0,36 | 0,33 |
| SD (s) | 0,62 | 0,69 | 0,62 | 0,88 | 0,76 | 0,64 | 0,60 | 0,57 |
| SE (sx) | 0,08 | 0,09 | 0,09 | 0,09 | 0,07 | 0,10 | 0,06 | 0,06 |
| Notes: 30.08 - 07.09: number of remaining old primaries (thus 1 = P10 still old). 18.09 - 30.09: number of new primaries (hence 6 = P6 full grown). *) By September, local argenteus get company from argentatus from Norway, which have on average lower moult scores and from argentatus from the Baltic region, which have equal moult scores probably. |
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