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 - 4cy /sub-adults June

Yellow-legged gulls and yellow-legged Herring Gulls in the Baltic
LARS JONSSON - Alula 3/1998

This is a copy of the article "Yellow-legged gulls and yellow-legged Herring Gulls in the Baltic", by Lars Jonsson and published in Alula 3, 1998. "I" in the text refer to the author Jonsson. We also reproduced some tables and figures from this article, but also added many, many more images from especially ringed birds to illustrate Lars's article. We did our best to be very precise, but if you find any errors, please let me know at marsmuusse at gmail dot com.

PART 1: Taxonomy & Nomenclature
PART 2: Field identification
PART 3: Caspian Gull
PART 4: Caspian Gull plumages
PART 5: Yellow-legged Gull
below: PART 6: Yellow-legged Gull plumages (last part)

Yellow-legged gulls and yellow-legged Herring Gulls in the Baltic

LARS JONSSON - Alula 3/1998

Yellow-legged Gull L. michahellis - subsequent plumages

The development into full adult plumage is generally completed by the time the third set of flight feathers is acquired, which means the autumn of the fourth calendar-year. In the autumn of the third calendar-year the sitting bird can already look almost like an adult and only brown marks on the primary coverts and dark markings on the bill reveal its immaturity.

First-summer
During the winter, early in its second calendar-year, it seems as if a variable amount of feathers are moulted for the second time (first pre-breeding moult), at least on some birds; these new feathers are quite similar to the first-winter ones, although some are cleaner grey at the base, giving a colder and smoother impression, but they are only rarely predominately grey. In mid-summer (while the flight feathers are being moulted) the upperparts are typically variegated and contrasting, with many intricate stripes, bars and dark blotches on scapulars and wing coverts, basically resembling argentatus, but more boldly patterned. Only a smaller percentage (ca. 20% in Hungary in late July) acquires unmarked grey scapulars. On average the head is lighter than on argentatus, but the dusky mask around the eye is typical throughout the second calendar-year. Cachinnans is usually more obviously white-headed at this age and acquires more or less white underwing coverts. By mid-summer of its second calendar-year, graellsii has acquired darker grey bases to many of scapulars (which also occurs in some atlantis) giving it an overall darker impression. Argentatus and cachinnans remain the most obvious confusion risk. Michahellis more often retains a dark iris at this age whereas argentatus commonly acquires a visibly lighter iris during the second winter (but can certainly be dark-eyed up to an almost adult stage).

Yellow-legged Gull michahellis M-015864 1CY, November 26 2006, Calais, France (Mars Muusse). From Switzerland. Dark streaking on head, breast and especially the woolly streaked hind-neck. Nearly all scapulars except some lower ones are moulted to second generation feathers, wing-coverts and tertials are still juvenile. The bill starts to get paler at base.	Yellow-legged Gull michahellis 2CY, February 18 2012, Zagreb, Croatia (Mars Muusse). Fresh upper scapulars now 3rd gen, again much 2nd gen-like in their patterns. Many inner wing-coverts and upper tertials replaced for 2nd gen feathers with bold dark centres, outer coverts still juvenile. Head feathers, neck, side of breast and flank replaced for 2nd gen feathers, head still with fine streaking.
Yellow-legged Gull michahellis 2CY, May 23 2012, Ebro Delta, Spain (Chris Gibbins). Active moult: P4 missing, P5-P10 old. Wing covert panel abraded, many scapulars adult-like grey.	Yellow-legged Gull michahellis 2CY, May 23 2012, Ebro Delta, Spain (Chris Gibbins). Active moult: Active moult: P2/P6.
Yellow-legged Gull michahellis M-002823 2CY, July 17 2007, Portalban, Switzerland (Stephane Aubry). From Switzerland. P1-P6 new, P9-P10 old. It is commonly seen that, while the outer primaries are replaced in the complete moult, a subsequent "partial autumn moult" will replace feathers in upper tertails and several inner wing-coverts in late summer and early autumn, which explains the fresher grey adult-like coverts seen in 2nd winter birds.	Herring Gull argentatus C237R 2CY, July 10 2003, Tampere, Finland (Mars Muusse). P1-P5 new, P8-P10 old.
Yellow-legged Gull michahellis G041 2CY, August 2010, Málaga, Spain (Gabriel Martín). Probably male. Note that new feathers have a creamy brown tone, and the old feathers have a bleached, faded pale base-colour. Facial mask is conspicuous. Still in complete moult: P7/-.	Yellow-legged Gull michahellis M-000754 2CY, September 01 2005, Hauterive, Switzerland (Stephane Aubry). From Switzerland. The partial moult started in this bird, note missing upper tertial. A partial autumn moult will normally replace feathers in upper tertails and several inner wing-coverts in late summer and early autumn, which explains the fresher grey adult-like coverts seen in 2nd winter birds.

Second-winter plumage
Second-winter (2nd – 3rd cy) birds are quite variable; many are still very immature looking in late summer / early autumn with much dark on the bill and strongly marked/barred wing coverts and scapulars. It seems that many others acquire plainer grey feathers later in the autumn (September-October?) on the mantle and scapulars, as well as median wing coverts. At least in the Baltic, argentatus never acquires plain grey wing coverts in the autumn of their second calendar-year. The great majority of argentatus does not show any plain grey feathers before around February of their third calendar-year, and even in the autumn of their third calendar-year they still have some dark-patterned scapulars. The underwing coverts are always well marked with brown in this plumage whereas in cachinnans it is usually almost white or has only fine rows of small spots.

Yellow-legged Gull michahellis M-000660 2CY, December 21 2005, Neuchâtel, Switzerland (Stephane Aubry). From Switzerland. Partial moult included upper TT, inner GC, inner + central MC and inner LLC and LC.	Yellow-legged Gull michahellis lusitanius 3CY, February 08 2011, Pontevedra, Spain (Quique Carballal). Typical pattern after partial autumn moult: last acquired feathers grey, incuding central MC, inner GC, upper TT and several LC.
Yellow-legged Gull michahellis 3CY, February 18-19 2012, Zagreb, Croatia (Mars Muusse). Grey saddle against barred lesser coverts. Median coverts replaced in partial autumn moult.	Yellow-legged Gull atlantis 3CY, July 25 2012, Canary Islands (Manuel Negrin). P5-P10 still old. Inner primaries growing.
Yellow-legged Gull michahellis 3CY, July 31 2011, Tarragona, Spain (Albert Cama). Active moult: P6 fully grown and P9-P10 still old. Note brown centres of secondaries (2nd gen), just visible underneath the gap in the greater coverts and the 2nd gen tail.	Yellow-legged Gull michahellis C? 7108 3CY, September 22 2007, Etaples, France (Jean Michel Sauvage). Complete moult: P8/-. New 3rd gen outer primaries sometimes brown without obvious tips, but very adult-like in this bird. Moult in tail almost finished.
Yellow-legged Gull michahellis S9UT 4CY, April 19 2011, Krk, Croatia (Wolfgang Schweighofer). Adult-like bird, with brown in tertials, but no black on bill.	Yellow-legged Gull michahellis S9YX 4CY, April 19 2011, Krk, Croatia (Wolfgang Schweighofer). Adult-like bird, with brown in tertials but limited black on bill. In flight, obvious immature bird.

Second-summer - third-winter plumage
The second pre-breeding moult may start as early as December, but at the latest by mid February the saddle in the vast majority of birds has become perfectly grey (fig. 23) and the head white. By March only few birds still show streaks on the head and a few brown-patterned feathers on the scapulars. The bill usually becomes lighter, dirty yellowish to clear yellow, with a black band or patch near the tip bordered with orange at the gonys. Birds in the summer of their third calendar-year all progress from a more or less immature look to an appearance more like that of an adult. They will however still have brownish outer greater primary coverts, reduced white on the wingtip and some still have dark vermiculation on a few tail feathers. Many third-winter birds may show some dark-smudged underwing coverts, like argentatus. The bill colour obviously regresses to become darker again after the breeding season.

Behaviour and vocalisation

Cachinnans is often dominant over argentatus when the two feed together. A few authors have described Finnish-ringed argentatus as being very dominant. This is possibly related to size, male cahinnans often being very big and the same may apply to some of the inland breeding argentatus in the Fenno-Baltic area. Cachinnans demonstrates its position by frequently stretching its wings and calling with the head raised vertically. This position, reminiscent of an albatross, is typically used during the longcall (see fig. 37). Argentatus and michahellis are less inclined to demonstratively raise their wings, but in close struggles for food or just after landing in a breeding colony, the wings can be lifted for a short time. Michahellis and cachinnans share with fuscus the very deep bow during the first phase of the longcall as well as the vertically raised head in its second part. Argentatus tends to stretch up the head at an angle of 45°. Both fuscus and michahellis however occasionally also call with a more argentatus-like angle. Any behavioural characteristics are usually of little value as fieldmarks if only observed once, but when a certain trait is persistently executed it can be a strong species indication.

Cachinnans has a peculiar, nasal sound to its voice; the longcall is faster, more of a staccato, and deeper and more nasal than that of argentatus. Larus cachinnans means the laughing gull and this is still the name in use in the Russian language.

Michahellis has a longcall which is close to fuscus in tone and rhythm. To my ear it is obviously slower than in cachinnans and deeper and more nasal than in argentatus, the longcall of which has a clearer and more musical voice.

Identification problems with other gulls: Lesser Black-backed Gull L. fuscus (Linne 1758)

Nominate fuscus of the Baltic Sea, northern Norway, Finland and the White Sea is, in adult plumage, unlikely to be ever mistaken for either cachinnans or michahellis, but in juvenile plumage they are more similar. The same can be said of intermedius of western Scandinavia and graellsii of Britain, Ireland and Iceland. Juvenile and first-winter graellsii especially can be very difficult to tell from michahellis and some individuals may be impossible to identify. The occurrence of the odd graellsii in the Baltic should not, however, in practise give rise to significant problems; it is clearly the odd argentatus that causes the most confusion here.

Yellow-legged Gull michahellis CC9273 1CY, September 01 2006, IJmuiden, the Netherlands (Mars Muusse). From Italy. Probably male. Many scapulars replaced.	Lesser Black-backed Gull graellsii 5T 1CY, September 12 2011, Boulogne sur mer, France (Jean-Michel Sauvage). From the Netherlands. Note slender bill.
Lesser Black-backed Gull intermedius JJ2T 1CY, September 20 2011, Westkapelle, the Netherlands (Maarten van Kleinwee). Juvenile plumage.	Lesser Black-backed Gull fuscus CYCE 1CY, September 06 2003, Tampere, Finland (Visa Rauste). Contrasting plumage; completely juvenile.

Identification problems with other gulls: Tundra/Siberian Gull L. heuglini (Bree 1876)

I do not intend to cover the identification of this form in any detail here. The regular presence of L. heuglini in Finland has become obvious over the past few years (Eskelin & Pursiainen 1998). This is not surprising, given the close proximity of the breeding grounds on the shores of the White Sea.
Adult heuglini shows a mantle colour usually varying between 9.0-10.0 (8.5-10.5) on the Kodak Grey Scale and is therefore unlikely to be confused with any of the light-mantled forms. Problems in distinguishing heuglini from michahellis and cachinnans respectively are most likely to arise in the case of immature birds which completely lack grey feathers in the mantle or scapulars. Theoretically juvenile heuglini could present an identification problem vis-a-vis cachinnans and michahellis; in practice however, by the time the first juvenile heuglini appears, in a perfect fresh plumage (September-October), the other two forms are considerably more advanced in moult and wear. Until an actual case arises I think this problem can be left aside.
In the spring the scene regarding misidentifying vagrant heuglini is somewhat different. Returning or wandering first-summer individuals of cachinnans, michahellis, heuglini, graellsii and possibly barabensis can due to large individual differences be very difficult to tell apart. The structural difference is always there but plumage wise heuglini and some cachinnans may be difficult to tell apart.

Heuglin's Gull heuglini 1CY, October 01 2011, Ashdod, Israel (Amir Ben Dov). Fresh juvenile plumage.	Heuglin's Gull heuglini 2CY, mid-June 2002, Syktyvkar, Russia (Visa Rauste). Cachinnans-like jizz, but fresh juvenile feathers.
Caspian Gull cachinnans PKZU 1CY, October 04 2012, Minden, Germany (Armin Deutsch). All scaps and single coverts replaced.	Caspian Gull cachinnans KE74 2CY, May 23 2007, Łubna, Poland (Ruud Altenburg). Bird in active complete moult, MC row missing, upper TT missing.

Acknowledgements

Many omithologist and friends have contributed to this article by supplying valuable information, photographs and general support. Especially thanks to Kenneth Bengtsson, Andrés Bermejo, Christian Cederroth, Martin Elliot, Jens & Hanne Eriksen, Andrei Filchagov, Goran Frisk, Eddie Fritze, Annika Forsten, Martin Gamer, Martti Hario, Andreas Helbig, Eric Hirschfeld, Ronald Klein, Dorit Liebers, Howard King, Hans Larsson, Harry J. Lehto, Henry Lehto, Klaus Malling Olsen, Dave McAdams, Killian Mullamey, Kjeld Pedersen, Pertti Saurola, Torsten Stjemberg, Ante Strand, Lars Svensson, Norman van Swelm, Lars Tydén and many more.

References (see PDF)