Herring Gull - Zilvermeeuw (argentatus & argenteus): 4cy June
(last update: 08 december 2003)
Herring Gull 4cy (argenteus), June 24 2003, IJmuiden, the Netherlands (52.27N,04.33E).
A 4cy argenteus. The scapulars and wing-coverts appear completely adult-like grey. The primaries show a clear mirror on P10. Last autumn, this individual has replaced the all-brown immature primaries for more adult-like primaries, which show a white tip, a grey basal half and one or two mirrors (P9 and P10). But still the size of the dark patches and the amount of black in the outer primaries is more extensive when compared to adults: there is often a broad dark sub-terminal band on P5 and a dark faint spot on the outer-web of P4. The dark patches are not sharply demarcated as in adult, but the dark outer-web gradually dissolves in the grey inner-web.
During summer, from June onwards, a
complete moult takes place in argenteus, bringing birds in
so-called "adult winter" plumage. As long as the old outer third
generation primaries are visible (until August), ageing as 4cy argenteus
is rather straightforward. From November onwards, 4cy argenteus
much resembles adult birds, except that the bare parts still show immature
feathers: the black bill-band is obvious, extending over both upper and
lower mandible. On average, this plumage develops a more pronounced winter
'hood' than in full adults: dense streaking on head, especially around the
eye and in the hind-neck. The upper-parts, wing-coverts and tertials
appear adult-like grey from 4cy October onwards. The fourth generation
tail-feathers are plain white.