Herring
Gull - Zilvermeeuw (argentatus & argenteus)
(last update: 08 december 2003)
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Herring Gull 365231 adult (argentatus), November 16 2002, Westkapelle, the Netherlands (51.33N-03.25E).
An adult argentatus, ringed with Norwegian Stavanger ring: 365231. The sub-terminal band on P9 is broken by the shaft and the white eats in into the black area on the outer-web, but not creating a complete thayeri-pattern. The band on P5 is limited to two small triangular spots on both inner-web and outer-web. A typical argentatus, with the upper-parts dark grey, obvious darker than local Dutch argenteus Herring Gulls, a coral red orbital ring, limited black in the outer primaries and a more powerful, stronger head and neck. Primary P9 is slightly shorter than P8. The moult stage of the primaries is behind compared to local Dutch argenteus. The inner wing-coverts and upper tertials still have relatively fresh fringes, in much better condition than found in some argenteus, which have these feathers replaced about 4 months ago and show worn fringes by November.
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 late November, the average argenteus in the Netherlands and northern
France has completely moulted all primaries. At the same time, the wing-covert moult is completed by the end
of the month. Argentatus from Scandinavia are behind in
primary moult.
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 in most argenteus, slightly darker, orange-red or
coral red in argentatus.
