Herring Gull - Zilvermeeuw (argentatus & argenteus): sub-adult November
(last update: 31 januari 2005)
Herring Gull sub-adult AF57, November 17 2002, Brouwersdam, the Netherlands (51.45N,03.51E).
A sub-adult ringed on the island Helgoland, Germany. A pale grey individual matching western argenteus in the grey tone of the upper-parts. But note the complete merged tip and mirror on P10 on this sub-adult bird, a feature more commonly found in argentatus. Note also the many barred wing-coverts, creating a clearer immature wing than in most argenteus. The birds on Helgoland may appear intermediate between argenteus and argentatus.
From June to October, sub-adult Herring
Gull have a complete moult to so-called "winter plumage".
As long as the old outer third generation primaries are visible (until
August), ageing as 4cy is rather straightforward. From November onwards,
4cy birds much resemble adult birds, except that the bare parts still show
immature features: 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.