Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: December 15, 2011 )

Coordinators:
Jean-Michel Sauvage (France)
Mars Muusse (the Netherlands)

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Herring Gull plumages:

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Herring Gull - 1cy November

Introduction

This website deals with the Herring Gulls of the taxa argentatus and argenteus. Argenteus is an abundant breeding species on Iceland, Britain, NW France, Belgium, the Netherlands and N Germany. The taxon argentatus breeds in NE Europe, from Denmark, the coast of the Baltic Sea, Scandinavia and coast of the White Sea. In the centre of the breeding range (Denmark and the NW German coast), birds show intermediate characteristics, indicating there is a cline in argenteus-argentatus. Argenteus in Western Europe is pale-backed, slightly smaller and with relatively much black in the wing-tip; argentatus in the NE Europe is larger, slightly darker on upper-parts and show less black in the wing-tip.
Due to the large breeding range, there is much intra-specific variation in argentatus, with most large, powerful birds in the northern populations, showing the most darkest upper-parts, longest wing and most white in the outer-wing. In this region, some populations may hold substantial number of yellow-legged argentatus. (referred to as "Finnmark yellow-legged argentatus"). In adult plumage, the black sub-terminal spot on P5 is often lacking or strongly reduced to a diffuse streak, broken at the centre. Sometimes P6 lacks black as well. 
In the Baltic region, other yellow-legged argentatus populations occur ("Baltic yellow-legged argentatus"), with adults showing even brighter yellow legs in summer and the upper-parts only slightly darker than West European argenteus, still much paler than Yellow-legged Gull (michahellis). Those Baltic argentatus often show a black sub-terminal spot on P5 in adult plumage.
On these web-pages, we largely follow P.J. Grant: "Gulls, a guide to identification" and E.K Barth's publication as Contribution No. 86, Zoological Museum, University of Oslo: "The circumpolar systematics of Larus argentatus and Larus fuscus with special reference to the Norwegian populations".

Comparison of 1CY November taxa:

graellsii 1K8 1CY, November 15 2009, Madrid, Spain (Delfín González). Dark greater coverts, overall chocolate brown tone, narrow fringe on tertials.	michahellis 1G6 1CY, November 15 2009, Madrid, Spain (Delfín González). Extensive post-juvenile moult in coverts and tertials finished.
marinus 97M 1CY, November 27 2013, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Heavy bill, small eye, short primary projection.	cachinnans PHUK 1CY, November 26 2011, Minden, Germany (Armin Deutsch). White-headed, all scaps replaced and commonly some coverts replaced. Often white underwing.
smithsonianus ALB 1CY, November 09 2013, Ocean City, MD (Clive Harris). Solid brown texture on underparts, heavily barred uppertail and undertail covert, almost all black tail.	smithsonianus 1CY, November 10 2012, Port Aransas, TX (Tripp Davenport). Probably bird from northern stock: scapulars still neat and almost all are juvenile.
argentatus J1490 1CY, November 27 2011, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Bird from northern stock: scapulars still neat and almost all are juvenile.	argenteus A5UW 1CY, November 09 2008, Boulogne-sur-Mer, France (Jean-Michel Sauvage). From the U.K. all scaps replaced, tertials deeply notched.

1cy Herring Gull: description for November

By November, NW European Herring Gull show obvious wear in wing-coverts, tail-tip and tertials. But birds hatched in northern Russia may still show a rather neat complete juvenile plumage, with the head and under-parts streaked grey-brown, rather pale on forehead and throat and with dark ear-coverts. The mantle and scapulars in these juveniles are brown based with buffish-yellowish fringes when the feathers are fresh. The notched pattern is repeated on the lesser, lower lesser and median coverts, although the medians often have paler centres. The greater coverts show a 'piano-key' pattern. On average, the tertials have an obvious notched pale fringe and transversal bar. This is more pronounced in argenteus than in argentatus. The secondaries, primaries and primary coverts are dark with a small white tip, but the inner primaries show an obvious, sometimes translucent, 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. Some argentatus show a broken tail-band, reminiscent to Great Black-backed Gull (L. marinus). The iris is very dark, the bill is blackish, sometimes with a paler base, and the legs are flesh-pink with dark shins.

1cy Herring Gull: post-juvenile moult

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 (especially in southern populations) and continues until January. Early argenteus juveniles fledge by late-June in the Netherlands, argentatus fledge mid-July in northern USSR. The post-juvenile moult is most extensive in southern Herring Gull populations and the final stage of this moult is more or less reached by mid November. Northern juvenile argentatus may postponed the post-juvenile moult until February, hence retain a juvenile plumage (e.g. this Russian 2cy argentatus in February).
In the post-juvenile moult, the head turns paler on throat and forehead. The breast turns paler as well, but most is an effect of bleaching and wear. The feathers on belly and vent remain juvenile in most 1cy argenteus by November. 
1cy November birds in NW Europe normally have the mantle, upper scapulars (100% second generation, i.e. category A in our research) and most lower scapulars moulted to second generation feathers (over 50%, i.e. category A-C), showing an anchor pattern and a dark base. This moult normally starts in the rear upper scapular region high on the back, and progresses downwards to the lower scapulars. The rear lower scapulars, which are the longest scapulars, lying on the scapular coverts, are normally still juvenile by February. When the feathers are fresh, they may show warm ginger tones, but after a few weeks these warm tones bleach paler, to white later in the season. 
In 2cy argenteus in NW France (from Belgian, Dutch and British populations), the lowest row of scapulars are still juvenile by 2cy March in the vast majority of birds (contra e.g. the southern taxon michahellis). Both argenteus and argentatus normally exclude all tertials and wing-coverts from the post-juvenile moult. However, we estimate 2-4% of argenteus to include one or a few wing-coverts or a single tertial in the post-juvenile moult (often in a later stage of this moult, when scapular moult is well underway). We don't have sufficient data to estimate for argentatus, but several pictures show this phenomenon in argentatus as well. The juvenile wing-coverts, rectrices and remiges start to bleach and show wear in the fringes from 1cy September onwards.

All 1cy argenteus and argentatus from S-Scandinavia show new feathers replaced in the post-juvenile moult by November. We do not get high northern birds early in autumn, but ringed bird in November - March show that these individuals may remain completely juvenile for a much longer period. Below, we included a table of 7 ringed argenteus, of which 1 bird already replaced all scapulars. This bird also replaced one wing-covert.
From a "definition point of view", we score this birds category F (0% 2g feathers) as the second generation feathers are still not visible. Only when these new feathers are visible, birds move to category E (1-24% 2g), as it is very hard to interpret missing minute upper scapulars in the upper region. On the other far end we have category A (100% 2g feathers) which is only used when the longest rear lower scapulars are dropped as well. These longest scapulars are the last to be moulted in the entire scapular region. Some birds already moult to third generation scapulars in the upper region, while these longest lower scapulars are still juvenile.

argentatus RUM C-730184 1CY, December 09 2010, IJmuiden, the Netherlands (Mars Muusse). Lower scaps still juvenile.	argenteus VLC 1CY, December 03 2012, Boulogne-sur-Mer, France (Jean-Michel Sauvage). From the U.K. all scaps replaced.
argentatus KV48 1CY, December 31 2006, Oostende, Belgium (Francois Roland). Lower scaps still juvenile.	argenteus YAMF 1CY, December 09 2010, IJmuiden, the Netherlands (Mars Muusse). Almost all scaps replaced.

1cy Herring Gull November: tables

below: a few unringed 1CY Herring Gull with limited scap moult by late-November.

Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.	Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.
Herring Gull argentatus 1CY, November 25 2016, Katwijk, the Netherlands.	Herring Gull argentatus 1CY, November 25 2016, Katwijk, the Netherlands.
Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.	Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.
Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.	Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.
Herring Gull argentatus 1CY, November 24 2016, Katwijk, the Netherlands.	Herring Gull 1CY, November 24 2016, Katwijk, the Netherlands.

rings argenteus: U.K.