Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 7-3-2007)

Herring Gull C525K 3cy (argentatus), August 11 2002, Tampere, Finland (61.31N,23.43E).

A 3cy argentatus, ringed as 3cy on August 11 2002 at Tampere, Finland: white C525K, with arm-length 440 mm. The complete moult is well underway with most wing-coverts and the inner primaries moulted to third generation. Primary P8 has been dropped and P9-P10 are still juvenile. P1-P6 are fully grown second generation flight-feathers and P7 equals P4. The outermost secondaries S1 has been replaced, the adjacent secondaries are missing, while the median and inner secondaries are still old second generation.
The upper tertials and the wing-coverts are replaced for third generation feathers (except the lesser coverts). The central greater coverts are still missing and growing: the gap in the greater covert row is almost closed. Almost all scapulars have been replaced for third generation feathers, including the scapulars in the lowest row. A few scapulars still have a brown hue.

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). 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.

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.