(2 images) Herring Gull H - 133730 2cy (argenteus), February 26 2004, Borselle, the Netherlands. Photo by Pim Wolf.

Ringed in Belgium as pullus in summer 2003, with metal ring Bruxelles H-133730. An individual with all scapulars moulted for second generation feathers (upper scapulars: 100% moulted, lower scapulars 75-99% moulted, total: class 75-99% moulted). The last moulted lower scapulars in the lowest row show feathers with a grey base and an anchor pattern 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 turns paler on throat and forehead, compared to the juvenile plumage. 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, after leaving the nest, the mantle and upper scapulars were moulted last year to second generation feathers, showing an anchor pattern and a dark base. The lowest row of scapulars, especially the rear feathers, are still juvenile or actively moulted by March in most 2cy birds (contra e.g. michahellis, which has finished the replacement in the lowest row). The notched pattern of the juvenile tertials, lesser, lower lesser and median coverts is not very obvious anymore by February, 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.