Larus cachinnans

(last update: February 16, 2013)

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1cy cachinnans: October

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".

First part: INTRODUCTION & IDENTIFICATION

Second part: JUVENILES (1CY birds in July–September)

Below, we continue with PART 3 "Birds in their first winter (1CY/2CY birds in October–April)". "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 winter (1CY/2CY birds in October–April)

At this age, cachinnans are arguably at their most striking and easy to identify (plates 59 & 60). The general impression is of a bird with an extremely white head and body, pale and rather delicately marked scapulars, and wing-coverts and tertials that, especially at a distance, look as though they have been painted softly in watercolours.

Larus cachinnans 1cy VP9Y December 12 2012, Damhus Sø -København, Denmark. Picture: Lars Krogh.

Larus cachinnans 2cy, 14 March 2012, Texel, the Netherlands. Picture: Herman Bouman.

By October, cachinnans has second-generation mantle feathers, scapulars and, in some birds, coverts and tertials, representing the progression from juvenile to first-winter plumage. Second-generation scapulars may be highly distinctive, typically showing a silvery-grey ground colour (paler grey than those of adults) with a simple dark shaft streak and either a rather diffuse subterminal anchor pattern or a dark basal diamond; most lack strong crossbarring. The silvery ground colour fades rapidly as the winter progresses and the dark markings become more subdued, leading to an increasingly pale and uniform-looking bird. On many cachinnans, the lowest row of second-generation scapulars appear paler and more lightly marked than the rest, and hence form a pale band separating the upper scapulars from the brown wing-coverts. Younger feathers in a moult sequence may differ in pattern from older ones (Howell 2001), which may explain the presence of this pale band.

Typically, michahellis are quite different (plate 61): their second-generation scapulars are strongly marked with heavy crossbars and a broad, dark anchor near the tip. The same relative differences occur on any new wingcoverts or tertials moulted in during the autumn: cachinnans usually have simple and subtle patterns, michahellis strong and bold ones. The pattern on the second-generation scapulars of Herring Gull is extremely variable (plate 62) but in broad terms is intermediate between that of cachinnans and
michahellis. The ground colour of each feather ranges from pale, sandy brown to mid brown, and most have darker crossbars and an anchor pattern towards the tip. It is extremely rare (perhaps unknown) for genetically pure Herring Gulls to have the silver tone and simple dark shaft streak of classic cachinnans. Importantly, however, a significant proportion of cachinnans have rather heavily marked second-generation scapulars (e.g. plate 63).

Larus michahellis 1cy, November 24 2006, Etaples, NW France. Picture: Ruud Altenburg.	Larus argentatus argenteus 1cy S.WAA 11 December 11 2011, Boulogne-sur-Mer, NW France. Picture: Jean-Michel Sauvage.
Larus cachinnans VC2L November 2009 & June 2010, Rødvig-Stevns, Sjælland, Denmark. Picture: Lars Krogh. Some Caspian Gulls, like this one, have rather heavily marked second-generation scapulars and overlap with Herring Gulls in this respect. However, note the characteristic jizz.	Larus cachinnans 2cy, March 08 2011, Ashdod, Israel. Picture: Amir Ben Dov. By early spring, some 1W Caspian Gulls are extremely pale and abraded, especially those that have wintered in hotter climates. The once blackish areas are faded brown and the sunbleached wing-coverts lack any clear pattern.

The striking appearance of many cachinnans during their first winter stems from a combination of the patterns on new second-generation feathers and wear on remaining first-generation ones. Wear is especially evident on birds reared earlier in more southerly and easterly areas, where sun bleaching and sand blasting (on dry beaches) take their toll on feather condition. Even in September, 1CY cachinnans around the Black Sea can be rather worn and shabby. Light 'pencil' streaking on the head and body progressively wears away, and can give rise to a startlingly white appearance, compared with Herring Gull. By midwinter, any remaining streaks are confined to a neat necklace around the lower rear neck. The white head isolates and emphasises the dark eye. Wear tends to simplify and thus emphasise the pattern on remaining first-generation greater coverts (dark base, pale distal bar) and, on some, the second pale bar (on the lowest row of median coverts) becomes prominent. The fact that this second bar is less frequently
apparent on the same feathers in late summer suggests that its prominence is related to wear and fading.

By spring, most cachinnans look a little paler than in autumn, with a more subdued contrast between the whites, greys, browns and blacks. The first-generation feathers can look rather washed-out, with the feather patterning less clear. For those individuals that included some coverts or tertials in the post-juvenile moult, these (now somewhat worn) feathers show up as discontinuities on an otherwise juvenile wing (plate 60). On some, pure grey feathers are distributed randomly across the scapulars (these may be third-generation feathers grown during the winter), giving an overall impression quite unlike Herring Gull; in fact, such advanced cachinnans (and especially those which also have some second-generation coverts and tertials) are more likely to be mistaken for a second-winter Herring Gull than a first-winter. The plumage of michahellis also fades over the winter and those that have retained their first-generation coverts and tertials can be a trap for the unwary. Despite their original notched patterns, the worn coverts of michahellis can become surprisingly uniform by spring. Similarly, tertial wear makes the feather pattern more difficult to discern and so it is effectively inseparable from that of cachinnans. The rangy appearance of some michahellis means that observers faced with a worn, putative cachinnans in the late winter/early spring period should be wary. Careful assessments of bill shape, head proportions, call and details of the underwing are critical at this time.

During their first autumn and winter, a small proportion of michahellis moult their tail feathers (certainly less than 20%, and perhaps less than 10%; Hannu Koskinen and Visa Rauste pers. comm., based on studies in Italy and Greece respectively). Herring Gulls (many thousands observed) and cachinnans in northwest Europe (c. 100 first-winters observed) normally do not, unless rectrices are lost or damaged. Thus, a late winter/early spring 2CY is unlikely to be cachinnans if it has new tail feathers – it will most likely be michahellis. However, the wintering range of cachinnans is large and, for example, those wintering in the Persian Gulf may follow a different strategy; insufficient data are available to assess this.

As the remiges and rectrices are not (normally) included in the post-juvenile moult of cachinnans, the wing and tail patterns of first-winters are the same as described above for juveniles. However, by late winter cachinnans tend to look paler in flight than in the autumn (as a consequence of wear and fading) and so the primary window or Venetian-blind effect often appears more contrasting. The underwing also looks paler,
more gleaming white and more sparsely marked than earlier in the winter (plate 64). This suggests that at least some underwing coverts and axillaries are dropped or replaced with pure white feathers over the winter.

Bare parts

The bill remains black with a variable amount of dirty pink on the basal portion. Close views may reveal a pale tip, which can suggest that birds have a diffuse, subterminal dark band. There is a tendency for cachinnans to have a more extensively pale bill than michahellis during the first winter, but this is far from diagnostic. The legs and irides are as described for juveniles.

END OF PART 3

CONTINUE AT PART 4: BIRDS IN THEIR FIRST SUMMER (2CY BIRDS IN MAY-SEPTEMBER)