Herring Gull- Zilvermeeuw (L. argentatus argenteus)

(last update: 04 december 2003)

Herring Gull argentatus
Herring Gull argenteus
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1CY ARGENTEUS
In juvenile plumage, the head and under-parts are streaked grey-brown, rather pale on forehead and throat and with dark ear-coverts. The mantle and scapulars are brown based with buffish-yellowish notches in the fringe when the feathers are fresh. The notched pattern is repeated on the lesser, lower lesser and median coverts. The greater coverts show a 'piano-key' pattern; on the outer greater coverts as well. The tertials have an obvious pale fringe and transversal bar. The secondaries, primaries and primary coverts are dark, but the 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 brown, the bill is blackish, sometimes with a paler base, and the legs are flesh-pink.

comparison of the three taxa of Herring Gull: juveniles from August.
juvenile argenteus	juvenile argentatus	juvenile smithsonianus

The partial autumn moult (moult 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. The breast turns paler as well. The feathers on belly and vent are still juvenile in most 1cy argenteus by November. The mantle and upper scapulars are moulted to second generation feathers, showing an anchor pattern and a dark base. The lowest row of scapulars are still juvenile by March in most 2cy birds (contra e.g. michahellis). The juvenile wing-coverts, rectrices and remiges start to bleach and show wear in the fringes.

comparison of the three taxa of Herring Gull: 2cy from January.
2cy argenteus	2cy argentatus	2cy smithsonianus

2CY ARGENTEUS
The next moult is a partial moult of head and body in spring. It starts in January and ends by May, leaving birds in so-called "first summer" plumage. The head and under-parts resemble the pattern in 1cy birds, although the head and breast turn much paler by June. The lower scapulars may still be moulted in this period, showing a buffish tone and a neat pale fringe. The adjacent juvenile rear lowest scapulars are very worn by March.

comparison of the three taxa of Herring Gull: 2cy from May.
2cy argenteus	2cy argentatus	2cy smithsonianus

From May onwards, a complete moult will bring birds in so-called "second winter" plumage by October. The head will show neat fine streaking by October; the under-parts and rump turns pale, mottled brown. The scapulars and mantle moult to third generation feathers, especially in the mantle and upper scapulars. The pattern is more or less similar to the anchor pattern of the second generation feathers, but can be recognized by the warm buffish tone and neat white fringe as long as the feathers are fresh. Only a few new scapulars may be pale grey adult-like feathers. By October, the upper scapulars are replaced and argenteus is actively moulting the lower scapulars, with still some old second generation rear lower scapulars. 
From late April, the wing-coverts and the very abraded tertials will be replaced, starting with the median coverts, upper tertials and innermost greater coverts. The fresh feathers are 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. 
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 under-wing is largely pale with pale brown barring. The second generation tail-feathers show a clear-cut blackish tail-band with only isolated blackish markings on the white basal half. The rump is largely white. The iris is pale brown. The bill shows a pale pinkish base with a dark tip. The legs are flesh-pink.

comparison of the three taxa of Herring Gull: 2cy from September.
2cy argenteus	2cy argentatus	2cy smithsonianus

According to Grant ("Gulls, a guide to identification"), the next moult in argenteus is a partial moult in spring (in 3cy birds). However, continental argenteus has a partial moult in autumn in second calendar year as well (click here for a clear example). The moult sequence in autumn in the scapulars is not completely clear, but from September onwards, 2cy argenteus may moult the upper tertials, innermost greater coverts and various amount of median coverts and sometimes lower lesser coverts to third generation feathers (some of them more adult-like in pattern). 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).

comparison of the three taxa of Herring Gull: 3cy from January.
3cy argenteus	3cy argentatus	3cy smithsonianus

3CY ARGENTEUS
The next moult is 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, creating a contrasting saddle, as most of the wing-coverts are still barred. The 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 still an obvious dark bill-band.

comparison of the three taxa of Herring Gull: 3cy from May.
3cy argenteus	3cy argentatus	3cy smithsonianus

From June to October, a complete moult will bring birds in so-called "third winter" plumage. In summer, the head is still largely white, but after the complete moult is finished, the head shows extensive 'winter streaking', mottled brown contrasting with the white breast as in an executioner's hood. The scapulars and mantle are pale adult-like grey, although some lower scapulars may show a pale brown hue. 
By mid-summer the old second generation wing-coverts are bleached, almost white, but by July the new third generation plain grey wing-coverts are moulted in, starting with the outermost median coverts. 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, most to plain grey feathers. Immature patterns can often be found in the lower tertials, greater coverts and outer lesser coverts (the carpal edge).
During the summer, the primaries are moulted to third generation. The first inner primaries are dropped by late May and the outer primary P10 is dropped by late August. The primary moult is completed by late-October, when the new outer primary P10 is fully grown. The third generation primaries are clearly adult-like, with the inner primaries P1-P4 plain grey and with a white tip. The outer-wing shows a clear black triangle, extending on the greater primary coverts. From P5 outwards, the primaries show a black sub-terminal band. The primary tips are obvious in the inner primaries, but only poor developed on P9 and P10. P10 has a small mirror (lacking in some birds). The tail-feathers are white, with clear immature black markings. The iris turns paler in summer (July).

comparison of the three taxa of Herring Gull: 3cy from September.
3cy argenteus	3cy argentatus	3cy smithsonianus

4CY ARGENTEUS
The next moult is a partial moult of head and body in spring. It starts in January and is completed by April, leaving birds in so-called "third summer" plumage. By April, the head and under-parts are white. The tail-feathers, wing-coverts and primaries are not replaced, therefore most birds strongly resemble "third winter"  birds, although the white primary tips wear away and dark patches start to bleach. The iris is yellow, the orbital ring yellowish-orange and the bill predominantly yellow with a red gonydeal spot and limited black markings along the culmen.

comparison of the three taxa of Herring Gull: 4cy from January-February.
4cy argenteus	4cy argentatus	4cy smithsonianus

From June to October, a complete moult will bring birds in so-called "adult winter" plumage. As long as the old outer third generation primaries are visible (until August), ageing as 4cy argenteus is rather straightforward. From November onwards, 4cy argenteus much resembles adult birds, except that the bare parts still show immature features: the black bill-band is obvious, extending over both upper and lower mandible. On average, this plumage develops a more pronounced winter 'hood' than in full adults: dense streaking on head, especially around the eye and in the hind-neck. The upper-parts, wing-coverts and tertials appear adult-like grey from 4cy October onwards. The fourth generation tail-feathers are plain white. 
The new fourth generation primaries are similar to the adult primaries, although the primary tips may appear slightly smaller, but otherwise similar in pattern: grey inner-wing and black outer-wing. Both P9 and P10 show a mirror. P5 shows small black sub-terminal markings, concentrated on the outer-web as a clear-cut black angular spot and rarely extending on the inner-web as a diffuse streak. There may be some black on P4 as well. Adult argenteus show a different pattern in the outer primaries, compared to northern argentatus. In argentatus, especially from northern Scandinavia, the black marking on P5 is very limited and diffuse or this is sub-terminal markings are completely lacking on P5. 
Argenteus has more black in the outer primaries, including a black band on the top of p10 in most birds, dividing the tip from the mirror. If the black sub-terminal band on P10 is broken, the outer-web of p10 still shows black marking. Argentatus normally lacks sub-terminal markings on the outer-web of P10. 
The scapular coverts are plain grey, lacking white crescents. The tertials show obvious white tips. The iris is yellow. The bill is yellow with a red gonydeal spot confined to the lower mandible. The orbital ring is yellow-orange or orange-red. The legs are flesh-pink.

comparison of the three taxa of Herring Gull: 4cy from August.
4cy argenteus	4cy argentatus	4cy smithsonianus

ADULT ARGENTEUS
The next moult is a partial moult of body and head in spring. It starts in January (when adults in the Netherlands may already return to the colonies) and is completed by April, leaving birds in so-called "adult summer" plumage. The head is clean white and the white primary tips are slightly worn and the dark patches bleached. Otherwise, this plumage much resembles the "adult winter" plumage. The bare parts are more saturated.

comparison of the three taxa of Herring Gull: adult from January.
adult argenteus	adult argentatus	adult smithsonianus

Measurements in mm’s wing: 375-447, tail: 152-189, bill: 45-58, tarsus: 55-70; n = 18 (origin of taxon unknown, Dwight, 1925).

ARGENTATUS & ARGENTEUS Herring Gulls are treated together. Click the thumbnails to go the monthly sections.