Herring Gull - Zilvermeeuw (argentatus & argenteus)

(last update: 08 december 2003)

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Herring Gull EJ adult (argenteus), August 15 2003, Westkapelle, the Netherlands (51.33N-03.25E).

A bird with a Dutch ring: mint green EJ at tibia, from the Moerdijk colony ringed by Roland-Jan Buijs.

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 August, the outermost primaries P7-P10, are still present in argenteus in the Netherlands and northern France. In most adults, the new primary P5 is just visible beneath the tertials. At the same time, the outer median coverts, outer lower lesser and innermost greater coverts have been renewed and contrast with the old, abraded adjacent wing-coverts. The central median coverts are still missing. In summer, the head is still largely white, but by the end of the summer, most adults develop extensive 'winter streaking', in sub-adults strongly mottled brown contrasting with the white breast as in an executioner's hood. The iris is yellow in adults. The bill is yellow with a red gonydeal spot confined to the lower mandible in the vast majority of adults. 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.

Remaining old primaries in adult (>4cy) Herring Gull in the Netherlands.
. 17.08.00 21.08.01 22.08.01 23.08.00 28.08.00 30.08.00
P10 - - - - 1 -
P9-P10 - - - 3 6 7
P8-P10 8 7 17 47 29 33
P7-P10 28 33 22 44 15 9
P6-P10 10 10 7 12 2 2
n: 46 50 46 106 53 51
m: 4,0 4,1 3,8 3,6 3,2 3,1
95% CID: 0,19 0,17 0,21 0,14 0,21 0,19
SD: 0,63 0,59 0,70 0,72 0,77 0,68

Notes:
17.08.00 & 22.08.01 scores from Bergen op Zoom, the Netherlands.
21.08.01 scores from Maasvlakte, the Netherlands.
23.08.00 scores from Le Portel, NW France.
28.08.00 & 30.08.00 scores from Scheveningen, the Netherlands.