Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 27-2-2007)

Herring Gull 3cy (argenteus), June 24 2003, IJmuiden, the Netherlands (52.27N,04.33E).

A 3cy argenteus with some immature dark feathers in the grey saddle and freshly moulted central and outer median coverts. Note that these fresh median coverts still show an obvious barred pattern. The second generation outer primaries are bleached brown without white tips and lack a mirror on P10. The second generation tail has a broad dark but bleached tail-band. 
This individual started the complete moult in the wing-coverts, as is obvious in the median covert bar, the inner greater coverts and several lesser coverts. Note the dark iris.

From June to October, a complete moult will bring birds in so-called "third winter" plumage. In summer, the head is still largely white, but after the complete moult is finished, the head will show extensive 'winter streaking', mottled brown contrasting with the white breast as in an executioner's hood. The scapulars and mantle are pale adult-like grey, although some lower scapulars may show an immature pale brown hue. 
By mid-summer the old second generation wing-coverts are bleached, almost white, but new third generation wing-coverts are moulted in, starting with the outermost median coverts. When inner greater coverts and median coverts were included in the partial autumn moult in 2cy, these feathers are left out of the moult sequence in the early moult-stage. By the end of the complete moult (October), all wing-coverts have been replaced, most to plain grey feathers. Immature patterns can often be found in the lower tertials, greater coverts and outer lesser coverts (the carpal edge).
During the summer, the primaries are moulted to third generation. The first inner primaries are dropped by late May and the outer primary P10 will be dropped by late August. The primary moult is completed  by late-October in argenteus, when the new outer primary P10 is fully grown. The third generation primaries are clearly adult-like, with the inner primaries P1-P4 plain grey with a white tip. The outer-wing shows a clear black triangle, extending on the greater primary coverts. From P5 outwards, the primaries show a black sub-terminal band. The primary tips are obvious in the inner primaries, but only poor developed on P9 and P10. P10 has a small white mirror (lacking in some birds). The new tail-feathers will be white, with clear immature black markings. The iris turns paler in summer (July).