Herring Gull 5.352.714 2cy-3cy (argenteus), July 10 2002 & March 17 2003, Boulogne/Mer, France (50.43N-01.37E).

below: Herring Gull 5.352.714 2cy (argenteus), July 10 2002, Boulogne/Mer, France (50.43N-01.37E).

A 2cy argenteus, ringed in the Netherlands, ring number Arnhem 5.352.714. It was ringed as pullus on July 02 2001 at IJmuiden (52.28N 04.35E). From late April onwards, argenteus has a complete moult during summer to so-called "second winter" plumage. This complete moult will be finished by October. The head appears white from May to July, will be moulted by July-August and will show neat fine streaking by October. The under-parts and rump turns pale, mottled with brown. From mid-April, the scapulars and mantle are replaced by third generation feathers, starting with the replacement of the lower upper scapulars. The pattern of the third generation scapulars is more or less similar to the anchor pattern of the second generation feathers, but they can be recognized by the warm buffish tone and neat white fringe as long as the feathers are fresh. In the second generation scapulars, the fringes are often worn away (especially in the upper scapulars). In argenteus, some new scapulars may appear adult-like pale grey, but most new feathers will show an anchor pattern and this still applies on the new feathers in September.

From early April, the inner primaries are shed and new second generation primaries grown in. The last juvenile primary (P10) will be shed by the first week of August. The majority of argenteus complete the primary moult by the first week of October, with a new second generation P10 fully grown. The new primaries are dark with a tiny pale tip on the fresh flight-feathers. Again, the four inner primaries show an extensive pale window, as both inner and outer-web are pale greyish white-brown, contrasting with the outer-wing. A pale inner-web can still be found in P7. 
The second generation tail-feathers will show a clear-cut blackish tail-band with only isolated blackish markings on the white basal half.
From late April, argenteus will replace the wing-coverts and tertials, starting with the median coverts, upper tertials and innermost greater coverts. The fresh feathers will be buffish-based with an obvious barred pattern. By July, the warm tones of the first moulted feathers are faded to plain white, leaving a contrasting barred pattern on the wing-coverts. The last coverts to be moulted are the central greater coverts, replaced by mid-August. The new greater coverts may show a vermiculated, densely barred pattern.
The primary moult score of Arnhem 5.352.714: P5 is fully grown and P9-P10 are still juvenile. The two upper tertials are replaced and the third is growing. The lower tertials are still juvenile. The four inner greater coverts have been moulted, #5 is still juvenile and much of the central greater coverts is missing. The outer greater coverts are growing in descendant order (from the outer-wing inwards). All median coverts fresh second generation feathers. The lower lesser covert row is a mix of fresh second generation feathers (#1, #3-5), some juvenile feathers (#2, #6-7) and growing feathers in the outer lower lesser row. About 50% of the lesser coverts have been dropped but the other 50% are still juvenile, mainly in the upper row and in the carpal edge. The fresh second generation scapulars can be found in the rear lower scapulars (second generation feathers), while the upper scapulars are moulting as well (to third generation).

below: Herring Gull 5.352.714 3cy (argenteus), March 17 2003, Le Portel / Boulogne-sur-Mer, France (50.42N,1.34E).

A 3cy argenteus, ringed in the Netherlands, Ringstation Arnhem 5.352.714. It was ringed as pullus on July 02 2001 at IJmuiden, the Netherlands (52.28N 04.35E). This individual represents the typical Dutch 3cy argenteus having the scapulars plain adult-like grey, contrasting with the barred lesser coverts, creating a saddle effect. In this individual, almost all scapulars are plain grey, except some rear lower scapulars. It also shows the typically pinkish base to the bill and a broad bill-band. The second generation primaries have small white crescents and lack the mirror on P10. The tail is completely second generation, showing a broad band.
The moult-stage is sometimes difficult to interpret in 3cy argenteus by March, but this Dutch bird obviously show moulted tertials and wing-coverts, replaced in the partial autumn moult as 2cy bird: tertials #1-3 have been replaced, greater coverts #1-3 have been replaced and some inner median and lower lesser coverts have been replaced (for anchor patterned or barred third generation feathers).

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.