(4 images) Herring Gull H - 117748 2cy - 3cy (argenteus), January 2002 - March 2003, Boulogne/Mer, France (50.43N-01.37E).

Metal ring Bruxelles H-117748, ringed as pullus on July 14 2001 at Zeebrugge (51.20N 03.11E). This bird was rediscovered in October 2002, at the same spot. Compare moult pace in these photo's. An individual with most scapulars moulted for second generation feathers. The last moulted lower scapulars in the lowest row show feathers with a grey base and two transversal bars on the top. The upper scapulars, which were moulted earlier, last autumn, are bleached by now and the buffish tones have turned white. 
The partial autumn moult in argenteus (moult from juvenile plumage into so-called "first winter" plumage) includes the body and head feathers. This moult starts as soon as the nest is abandoned (late June) and continues until January. In general, the head is paler on throat and forehead. The second generation feathers on the breast are paler as well. The feathers on the vent and the under-tail coverts are still juvenile in most 2cy argenteus by January. From July onwards, the mantle and upper scapulars were moulted to second generation feathers, showing an anchor pattern and a dark base. The lowest row of scapulars are still juvenile or actively moulted by March in most 2cy birds (contra e.g. michahellis). The notched pattern of the juvenile tertials, lesser, lower lesser and median coverts is not very obvious anymore, as the white parts are largely worn away. The juvenile greater coverts show a 'piano-key' pattern in argenteus; on the outer greater coverts as well. 
The secondaries, primaries and primary coverts are dark with a small white tip, but the juvenile inner primaries show an obvious pale window, prominent from below and above. The under-wing is rather uniform grey-brown patterned. The tail has a broad sub-terminal band and isolated dark bars on the basal half. The iris is dark, the bill is blackish, sometimes with a paler base, and the legs are flesh-pink.

photos above: H - 117748 2cy, January 04 2002, Boulogne/Mer, France (50.43N-01.37E).

photo below: H - 117748 2cy, October 24 2002, Boulogne/Mer, France (50.43N-01.37E).

The Belgian-ringed H-117748, was seen again by October, at the same spot. Throughout the summer, all feathers were replaced for second generation feathers. The complete moult has been finished, as P10 is fully grown. From late September to October, 2cy argenteus has a partial moult including some of the wing-coverts, tertials and probably some of the scapulars as well (the exact moult sequence and age of the scapulars is difficult to ascertain in autumn 2cy argenteus). This moult to third generation wing-coverts may overlap with the replacement to second generation feathers (the last replaced coverts: upper lesser coverts and the seventh and eighth greater coverts). H-117748 has replaced some feathers as well: tertials #1-3 are replaced in the partial autumn moult, greater coverts #1-3 are replaced, median coverts #1-3 are replaced, while #5 is still missing, and again #6-12 are replaced, and #14 is replaced. Replaced in the lower lesser coverts: #2 and #5-6. One lesser covert is growing. The last moulted third generation coverts have a grey base and an anchor pattern.

3 images below: H - 117748 3cy, March 17 2003, Boulogne/Mer, France (50.42N,1.34E).

A typical argenteus, with most scapulars plain adult-like grey, contrasting with the barred lesser coverts and creating a saddle. The bill is typical for 3cy birds in January, pinkish base and a broad bill-band. Note the rather brown second generation primaries lacking the mirror on P10. The tail is completely second generation, showing a broad band. Compared to Scandinavian argentatus, the general impression resembles argentatus in 4cy, which also show an almost complete grey scapular region and single grey feathers in the tertials, inner greater coverts and a few lesser coverts.
The moult-stage is sometimes difficult to interpret in 3cy argenteus by March. The scapulars are more or less uniform grey with just a few patterned brownish feathers left. Many grey scapulars appear abraded at the fringes already, especially in the upper scapulars.
This Belgian individual has moulted a few tertials and wing-coverts in the partial autumn moult as 2cy bird, as can be seen in the October image.

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. The head turns white, especially on throat, breast and belly. By April, the scapulars and mantle will show many adult-like grey feathers, often creating a contrasting "grey saddle", as most of the wing-coverts (especially the lesser coverts) are still barred. The old second generation wing-coverts start to fade and the fringes wear off. 
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.