Herring Gull - Zilvermeeuw (argentatus & argenteus): sub-adult Nov.
(last update: 07 april 2004)
Herring Gull 5cy AVAW, November 15 2003, Westkapelle, the Netherlands (51.33N-03.25E).
A 5cy from the Belgian colour-ring program, ringed blue AVAW. Ringed as pullus at Zeebrugge, Belgium (51.21N 03.11E) on July 09 1999. The primaries are very adult-like, with the mirror merged with the tip on P10. The tail is completely white. The last vestiges of immaturity are shown by the bare parts, especially the bill.
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.