Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 7-3-2007)

Herring Gull C5J54 3cy (argentatus), August 12 2002, Tampere, Finland (61.31N,23.43E).

A 3cy argentatus, ringed white C5J54 as pullus on June 22, 2000 in Vkoski, Finland. The complete moult is well underway with most wing-coverts and the inner primaries moulted to third generation. Primary P1-P6 are fully grown second generation flight-feathers and P10 is still juvenile. As the central greater coverts are dropped, the old second generation central secondaries underneath are visible: with brown extensive centres and a small white fringe.
The upper tertials and most of the wing-coverts are replaced for third generation feathers (except the central greater coverts and lesser coverts). Almost all scapulars have been replaced for third generation feathers, including the scapulars in the lowest row. A few grey scapulars have the fringes worn. 
Note the strong difference in patterning between the outer (grey) and central median coverts (barred), either a result of moult timing or differentiated by the fact that some feathers were previously included in the partial moult in autumn, and subsequently one generation ahead.

From June to October, a complete moult will bring 3cy argentatus in so-called "third winter" plumage. By August, the first neat streaks can be found on the crown and neck. After the complete moult is finished in autumn, the head will show extensive 'winter streaking', often neat fine streaking in argentatus and mottled brown contrasting with the white breast as in an executioner's hood in many argenteus. 
The scapulars and mantle are pale adult-like grey, although some individuals may show an immature pale brown hue or arrow-head patterns on the lower scapulars. 
From July onwards, the new third generation plain grey wing-coverts are moulted in, starting with the outermost median coverts. Contrary many argenteus, 3cy argentatus often show immature patterns on the inner greater coverts, inner and outermost median coverts and upper tertials (the first moulted wing-coverts and tertials in the complete summer moult). By the end of the complete moult (October), all wing-coverts have been replaced.

During the summer, the primaries are moulted to third generation. In argenteus, 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. First data from Tampere, Finland, indicate 3cy argentatus from this region are not delayed in primary moult compared to argenteus from NW Europe. The third generation primaries are clearly adult-like, with the inner primaries P1-P3 plain grey with a white tip. The outer-wing shows a clear black triangle, extending on the greater primary coverts. From P4 outwards, the primaries show a black sub-terminal band. The white primary tips are obvious in the inner primaries, but will only be poor developed on third generation P9 and P10. The third generation P10 will show 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 in most argenteus (July-August), but quite some argentatus will keep the iris amber to dark brown.