Larus cachinnans

(last update: February 16, 2013)

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2cy cachinnans: September

In 2010, Chris Gibbins, Brian J. Small and John Sweeney published two extensive papers in Britsih Birds, dealing with Caspian Gull. Below, you will find the content of the first paper "Part 1: typical birds".

Part 1: INTRODUCTION & IDENTIFICATION

Part 2: JUVENILES (1CY birds in July–September)

Part 3: BIRDS IN THEIR FIRST WINTER (1CY/2CY birds in October–April)

Below, we continue with PART 4 "Birds in their first summer (2CY birds in May–September)". "we" in the text below refers to the original authors. If any errors occur in this text, please let me know and mail to marsmuusseatgmaildotcom.

Birds in their first summer (2CY birds in May–September)

Larus cachinnans 2cy, August 2008, Riga, Latvia. Picture: Chris Gibbins. This is an example of the more distinctive plumage type seen in late summer, with some silvery-grey (probably third-generation) mantle feathers and lower scapulars on the right side. The greater coverts are a rather uniform mid brown. The new (dark) second-generation primaries have much more rounded tips than the remaining first-generation ones. This large, elegant bird should not pose any identification problems.

Larus cachinnans 2cy, 04-12 September 2009, Preila, Lithuania. Picture: Chris Gibbins.

Larus michahellis 2cy PDYZ August 15 2009, Tarragona, Spain. Picture Chris Gibbins. Last stage of complete moult: P8 fully grown, no old juvenile primaries left. First-summer michahellis show bewildering variability. This bird is a rather typical example of the more heavily marked type.

Larus michahellis 2cy G0.41 August 2010, Málaga, Spain. Picture: Gabriel Martín. P7 fully grown, no old juvenile primaries left. The plumage is quite different from 2CY Herring Gull (e.g. some clear grey scapulars) but overlaps to some degree with cachinnans. Best separated using jizz and the pale eye.

Moult

At some point in the spring or early summer, 2CY cachinnans drop their innermost primary; this signals the start of their first moult of the wings and tail. In large gulls, what was traditionally seen as the first complete moult (e.g. Grant 1986) is now regarded as the continuation of a cycle of moult that starts in autumn with the partial, post-juvenile moult (e.g. Howell 2001). Large gulls in western Europe generally do not moult during mid-winter, so there is a clear break between the end of post-juvenile moult and the start of wing and tail moult several months later. However, some 2CY cachinnans in the Middle East do moult in winter (pers. obs. CG). Moult has not been studied intensively in cachinnans and it is difficult to be sure whether the species' post-juvenile and first complete moults are best regarded as two separate events or part of the same continuous cycle. What is clear is that the identification of worn, faded 2CY birds in spring does not necessarily become easier once they start moulting – as with both Herring Gull and michahellis, the pattern on new feathers varies enormously from bird to bird and truly diagnostic markings are lacking.

Separation of cachinnans, michahellis and Herring Gull is arguably most difficult during the summer moult period. This is because, once in heavy moult, all three species can look tatty, and their jizz is affected by missing feathers. In Britain, the difficulty of separating these three species at this time is compounded by the fact that many birders are unfamiliar with the identification of worn and/or moulting first-summers because they spend more time looking at gulls in the winter. Importantly, many Herring Gulls look white-headed at this time, so a white-headed appearance is not a particularly useful identification feature.

Herring Gulls of this age are variable, but typically rather dull and nondescript. The head of 1S Herring Gull often lacks streaks, so a white-headed appearance is shared with cachinnans at this time of year and is not an important identification feature for this age group.
Larus argentatus argenteus 2cy 5.426.594 August 30 2010, Westkapelle, the Netherlands. P8 fully grown, no old primaries. Upper tertial, inner gc and mc missing again, indication for commencement of the partial autumn moult (which may overlap with last stage of complete moult).	Larus argentatus argenteus 2cy GNAZ August 22 2008,Boulogne/Mer, NW France. Picture: Jean-Michel Sauvage. Ringing data: GNAZ ringed as pullus at Oostende, Belgium, 13 July 2007.

Plumage

New scapulars grown during the summer may be grey and hence adult-like, but other birds show heavy spotting and anchoring; the same applies to new lesser and median coverts. The new tertials and greater coverts have a rather more consistent pattern, and to a degree resemble first-generation ones. On many cachinnans the new tertials have a plain, dark brown base and a diffuse, offwhite distal portion. The greater coverts generally lack strong barring and anchoring, instead having a rather uniform greyish to mid-brown wash basally and a diffuse pale fringe and finely vermiculated tip. As with first-generation feathers, there is a pale bar across the greater coverts and often also on the lower medians. The greater-covert and tertial patterns are unlike those of the most distinctive michahellis, which have strong blackish crossbars and anchors on otherwise pale feathers, and unlike those of Herring Gulls, which have a similar pattern to michahellis but more subdued.

By September, it is possible, in very general terms, to recognise two 'types' of 2CY cachinnans and michahellis (plates 67 & 68). Advanced birds have extensive, clean grey scapulars, wing-coverts and tertials, while less advanced types are heavily spotted and barred in these areas. The former are very
mature-looking compared with 2CY Herring Gulls, while the latter share a number of features with them. With less advanced birds, observers should not be looking for individually diagnostic features; identification should be based on structure, voice and subtle plumage clues.

Bare parts

Most 2CYs develop extensive pale areas on the bill by summer; the colour is highly variable, from rather bright pink, through dirty greyish-flesh to yellowish-grey. The legs appear flesh-coloured, sometimes with a grey cast. Eyes are invariably dark-looking (the iris is brown).

Larus cachinnans 2CY 080P May 25 2007, Lubna, Poland. Picture: Ruud Altenburg.

Larus cachinnans 2cy V453 June 11 2009, Simrishamn, Sweden. Picture: Jörgen Bernsmo.

Larus cachinnans 2cy, August 2008, Riga, Latvia. Picture: Chris Gibbins.

Larus cachinnans 2cy, 10 September 2009, Preila, Lithuania. Picture: Chris Gibbins.

END OF PART 4

CONTINUE AT PART 5: BIRDS IN THEIR SECOND WINTER (2CY/3CY BIRDS DURING OCTOBER-APRIL)