Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 27-2-2007)

(2 images) Herring Gull H-105381 3cy (argenteus), June 13 2002, Boulogne/Mer, France (50.42N,1.34E).

This 3cy argenteus was ringed as pullus on June 16 2000 at Zeebrugge, Belgium (51.20N 03.11E): Bruxelles H-105381. It shows the ordinary features for argenteus in June: The scapulars create an all-grey saddle. It strongly contrasts with the old faded brown-white chequered wing-coverts and dark centred tertials. 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 tail-band.

3cy argenteus has a partial moult in spring. It starts in January and is completed by April, leaving birds in so-called "second summer" plumage. By May, the head is white, especially on throat, breast and belly. The iris and base of the bill turn pale yellow, although some individuals show a warm amber iris. The bill shows some red on the gonydeal angle and it still shows an obvious dark bill-band.

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 shows 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 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 paler in summer (July).

This individual included the two upper tertials and some wing-coverts in the partial moult last autumn. One central median covert stands out as an all grey feather. The primary moult stage: P1-P3 are missing, P4-P10 are old second generation flight-feathers. Note the bill colour.