Larus cachinnans

(last update: February 16, 2013)

Greg Neubauer
Marcin Przymencki
Albert de Jong
Mars Muusse


3cy 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 2: JUVENILES (1CY birds in July–September)

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

Part 4: BIRDS IN THEIR FIRST SUMMER (2CY birds in May-September)

Part 5: BIRDS IN THEIR SECOND WINTER (2CY/3CY birds during October-April).

Below, we continue with PART 6: Older immature plumages (3CY–5CY birds). "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.

Older immature plumages (3CY–5CY birds)

Moult and plumage development
The second complete moult takes place during the summer and autumn of the third calendar-year and brings in new, pure grey feathers to the mantle, wing-coverts and tertials. The third-generation primaries have small white tips (unlike first- and second-generation ones), as well as large mirrors on P10 and, most frequently, also on P9. The outer primaries are otherwise blackish and the inner ones have adult grey tones. Once this moult is complete, birds can be regarded as being in third-winter plumage (here, here & here) and, overall, they show a greater resemblance to adult than earlier immature plumages. The upperparts are largely grey, with variable amounts of brown retained in the tertials and coverts. This plumage is retained over the winter and following spring/early summer, when the third complete moult takes place. This brings fourth-generation primaries and fully adult upperpart tones; normally, the only traces of immaturity are dark marks in the primary coverts and on the bill. The following text deals primarily with third-winter birds, but provides some information and illustrations of fourth-winter individuals.

Larus cachinnans
3cy, 10 September 2009, Preila, Lithuania. Picture: Chris Gibbins. This bird is near to the end of its moult into 3W plumage (the outer primaries are not quite fully grown). A number of subtle features, used collectively, make 3W Caspian Gulls rather distinctive, but as all are found from time to time in Herring Gulls, none are diagnostic.This bird show 'lead shot' eyes, contrasting with a clean
white head, greeny-yellow bill and grey-flesh legs.

Larus cachinnans 4cy, 10 April 2009, Riga, Latvia. Picture: Chris Gibbins. The extent of any brown remaining in the wing of this age group is variable – this bird has rather a lot of dark in the coverts, but
none in the tertials.

Larus cachinnans 4cy, February 08 2010, Riga, Latvia. Picture: Chris Gibbins. A bird with soft, greybrown patterning in the coverts and some brown remaining in the tertials. All the plumage features and bare-part colours visible in this bird can be found from time to time in Herring Gulls, so it illustrates nicely the fact that identification of birds in this age group should be supported by structure and, ideally, voice.

Larus cachinnans sub-adult, February 26 2011, Ashdod, Israel. Picture: Amir Ben Dov. The primary pattern of this bird is beginning to take
on some of the features of adults – note the grey
tongues eating into the black wing-tip. The outer
primary coverts and the alula retain extensive,
blackish-brown marks.

Once the second complete moult is finished (and third-winter plumage attained), the mantle and scapulars are generally adult grey, while the coverts are most frequently a mixture of grey and creamy-brown. There is much variability in the coverts, with some birds having wholly grey feathers. Brown feathers tend to be retained more in the marginal and lesser coverts, with the medians and greaters being contrastingly grey. The tertials are either all adult-like or have some brown patches. The outer primary coverts and the alula also retain extensive, blackish brown marks (plate 82). The secondaries of some birds have small, neat brown centres forming a broken bar. The tail pattern is extremely variable. Frequently there is an obvious vestigial tail band created by isolated black spots, rather like that of second-winter Ring-billed Gull L. delawarensis; such tail bands also occur in michahellis but are very rare in third-winter Herring Gulls. Some third-winter cachinnans, however, have a wholly white tail.

Although not yet the full adult pattern, the third-generation primaries of cachinnans offer useful identification clues. There is a broad, complete black band across P5 and usually some black on P4, either on both webs or just the outer. Third-winter birds that have limited or no black on P5 are unlikely to be cachinnans or michahellis. The white mirror on P10 can be a useful distinction from michahellis: in terms of size and prominence, the P10 mirror of most third-winter cachinnans matches that of an adult michahellis (much larger than on third-winter michahellis, which have either no mirror or only a small one). Most third-winter cachinnans also show a white mirror on P9, unlike michahellis (but see plate 84). Third-winter Herring Gulls can also show a reasonably large mirror on P9 and P10; argentatus can show a long white tip to P10, with only a small dark subterminal smudge (plate 86). Thus, the patterns on P9 and P10 are not diagnostic of third-winter cachinnans and are more useful for ruling out michahellis than Herring.
argentatus Herring Gulls in 3W often show extensive brown wash to the wings, a well-streaked head, have only limited black on P5 and (already) a very pale eye. Individually and collectively, these features make confusion with cachinnans unlikely. 3W argenteus Herring Gulls regularly show a complete, deep black band across P5. So, the presence of a black band on P5 is not a key feature at this age. Note that P10 is not yet fully grown by November in many northern argentatus.
Larus argentatus argentatus 4cy, February 07 2013, Katwijk, the Netherlands. Picture: Mars Muusse. Larus argentatus argentatus 3cy, Katwijk, Netherlands, 17 November 2009. Picture: Mars Muusse.

On some third-winter cachinnans, the middle primaries (P6–P8/P9) have black that extends further up the outer web than the inner; this gives the impression of grey 'tongues' cutting into the black of the wingtip, a pattern that develops more strongly in adults. This is very different from argenteus Herring Gulls and especially michahellis (plate 84), both of which show a solid, triangular black wedge across the wing-tip. Not all cachinnans have the distinctive tongued pattern, and so match michahellis and Herring Gull. Both cachinnans and michahellis show dark marks on the alula and primary coverts, which tend to be blacker and more clearly defined than in Herring Gull.

The head of cachinnans tends to be clean white, lacking distinct streaking. In autumn and early winter, a relatively neat half-collar of dark streaks is usually visible on the hindneck and can make cachinnans distinctive even at a distance. This streaking wears away as the winter progresses. Herring Gulls have more widespread, diffuse and blotchy head and neck streaking. The head streaking of 3CY–4CY michahellis in winter is often concentrated around the face rather than restricted to the hindneck.

In the summer of their fourth calendar year, the third complete moult brings in fourth-generation primaries. Once this is complete, birds are generally regarded as being fully adult, although some retain dark markings on the bill and black in the primary coverts and at the tip of P10. Confident ageing of such birds is difficult, however, since dark marks in the primary coverts and small areas of black in the bill are occasionally retained well into full adulthood. The fourth-generation primaries of cachinnans are similar to those of adults, with a long white tongue on the underside of P10 and grey tongues eating into the black wing-tip
on the upperside of P8–P10.
Larus michahellis lusitanius 3CY, Ares beach, NW Spain, November 27 2009. Picture: Antonio Gutierrez. There is some variation in the michahellis group, with "lusitanius" birds on the Atlantic coast of the Iberian peninsular. They often look slimmer and more elegant, lacking thefierce angular head shape of many michahellis, and this, compared to the more slender bill may sometimes give birds a cachinnans-look. However, note the rich yellow tones in bare parts in this November bird, something that will be more and more obvious in spring birds. Larus michahellis 4CY, January 26 2011, Istanbul, Turkey. Picture: Volkan Donbaloğlu. Birds of this age are variable.This one has an obvious mirror in P10 but on others it is much smaller or even lacking. It has a clean white tail but many retain vestigial dark marks. The extensive blackish-brown primary coverts contrast with the otherwise grey upperwing. The black of the primaries forms a solid wedge on the outer wing in michahellis.

Bare parts
The third-winter bill has a mix of blackish brown and paler areas. Black is usually confined to the gonys region as a diffuse 'thumbprint', with a paler tip and basal third to the bill. Some isolated darker smudges are often present closer to the base, and many have a little black bleeding along the cutting edge from the gonys. The pale parts of the bill are most frequently a dull greeny yellow, typically with a strong grey cast. Some have rather more yellow-toned bills. Red is not prominent in the gonys of cachinnans of this age. The legs are invariably a rather colourless, dead-flesh grey, compared with the pinker legs of Herring Gulls. The legs of third-winter michahellis are usually greeny-yellow or grey-yellow, with some having clear yellow tones; they can, however, occasionally be dull flesh-coloured as in cachinnans. The eyes of most cachinnans still look dark brown, but slightly paler irides may develop from this age onwards. Most but not all michahellis and Herrings of this age have paler (greeny- or greyish-yellow) eyes. It is rare for cachinnans of this age to have very pale (cream or yellow) eyes, and such birds should be scrutinised closely. Eye-ring colour tones of third-winter birds also begin to reflect those of adults (see below).

Despite often looking distinctive, third-winter and third-summer birds have no truly diagnostic plumage features. In essence, the distinctive features of younger birds have been lost, while the adult wing-tip pattern has not developed sufficiently for it to be considered critically important. Identification should be based on a careful assessment of structure, in combination with indicative plumage features listed above, and the absence of anomalies.

Some cachinnans of this age can be particularly tricky to separate from michahellis. Near-adult michahellis often have dark eyes and smaller individuals can have bill shape and overall jizz reminiscent of some cachinnans. Some cachinnans lack grey tongues in their third-generation primaries and so overlap with michahellis; however, they should have larger mirrors than michahellis. Long call and associated posture are the best way to separate the more difficult individuals.

Experienced gull-watchers are unlikely to mistake third- and fourth-winter Herring Gulls for cachinnans, but others should be aware of the problem posed by argentatus. Some late-winter argentatus are clean-headed
and share some aspects of the cachinnans wing-tip pattern – with a long white tip to P10 and grey tongues that invade the black wing-tip. While the irides of most Herring Gulls will be rather pale by their third winter, a significant proportion retain dark eyes: a clearly pale eye in a near-adult gull is not good for cachinnans but a dark eye does not automatically rule out Herring Gull.



Larus cachinnans 2CY-5CY UKK T-001874 May 2010 - July 2013, Windheim & Deponie Pohlsche Heide - Minden, Germany. Picture: Armin Deutsch.
Larus cachinnans hybrid? 2cy-3cy PLG DN-25884 October 2009 & September 2010, Westkapelle, the Netherlands. Picture: Theo Muusse.
Larus cachinnans 2CY-3CY SKB E1711 January 2013 - September 2014, the Netherlands & Germany.
Larus cachinnans 3cy, 04-12 September 2009, Preila, Lithuania. Picture: Chris Gibbins.
Larus cachinnans 3cy, 04-12 September 2009, Preila, Lithuania. Picture: Chris Gibbins.
Larus cachinnans 3cy, 04-12 September 2009, Preila, Lithuania. Picture: Chris Gibbins.
Larus cachinnans 3cy, 04-12 September 2009, Preila, Lithuania. Picture: Chris Gibbins.
Larus cachinnans 3cy, 04-12 September 2009, Preila, Lithuania. Picture: Chris Gibbins.
Larus cachinnans 3CY, September 24 2010, Westkapelle, the Netherlands. Picture: Maarten van Kleinwee.