Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 27-2-2007)

Herring Gull 3cy H-xxxxxx (argenteus), July 11 2002, Boulogne/Mer, France (50.42N,1.34E).

A bird with a Belgium ring: Bruxelles H-??, maybe the same birds as H-105381? Moult in the coverts has started with the outer medians and some lesser and lower lesser coverts. The scapulars and mantle feathers create a grey saddle on the back. The primary moult stage: P5 is missing. Note the bill colour.

From June to October, a complete moult will bring 3cy argenteus in so-called "third winter" plumage. By July the head is still largely white, but after the complete moult is finished in autumn, 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 individuals may show an immature pale brown hue on the lower scapulars. 
By mid-summer the old second generation wing-coverts are bleached, almost white, but by July new third generation plain grey 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 pale yellow in summer (July).