Lesser Black-backed Gull (graellsii & intermedius)

(last update: 09-06-2013)

third calendar year: June

Second summer (third calendar year) LBBG normally show a grey saddle on mantle and scapulars. In almost all birds, some of the coverts have been moulted into third generation. Sometimes the entire median covert row has been replaced, creating a grey bar. There seems to be small variation in birds of this age class. The feathers showing most variation are the rectrices; it might be anything from a clear tail-band, spaghetti pattern, black-and-white variegated pattern to a complete snow white tail (although close examination often reveals small black spots near the feather centre). Most advanced individuals seem to be slightly darker and more elongated; they probably originate from intermedius populations. Note however that a bird ringed in Norway has been recovered in the Maasvlakte colony, where it actually bred. Dutch colour rings have been found in Scandinavia in reverse.

Detailed description of  3cy LBBG in June

Mantle and scapulars

By June, adult-like grey feathers replace brown-hued old scapulars, probably at least for the third time, resulting in a fourth generation scapular region. Some old scapulars show a faint anchor pattern on a brown base.

Moult of coverts

By June, only the minority of 3cy LBBG starts moulting the median coverts. New third generation coverts are easily recognized as grey adult-like feathers. The old retained second generation feathers (plus the few third generation which were required in the last autumn moult) at least show some brown in the centre and a white fringes, though the exact pattern gets lost by wear.

Tail-feather moult

The exact rectrices-moult is often difficult to ascertain. Most commonly seen at this age is a worn second generation tail, i.e. a tail with black marks or tail feathers with a broad black tail-band. Only a few birds are actively moulting tail-feathers, starting with the innermost pair (R1, these are the feathers most exposed to sun and weather conditions). About 30% of 3cy LBBGs has moulted one or more pairs of tail-feathers last winter, giving them the blocked pattern of black and white feathers. This winter moult in the tail involved rectrices randomly, creating an unpredictable black and white tail in spring.

Remiges moult

  At the start of June some birds have already shed P1, while at the end of June most birds have P2 replaced and P4 shed. New third generation primaries are very adult-like (adult-grey with white tip) and differ clearly from the plain black-brown second generation primaries. 
The differences with real adult primaries can be found in the tips which are normally smaller in third generation primaries, P9 normally lacks a mirror, P10 has a smaller mirror and there is an extensive amount of black on P3 and P4 (more than on pure adult primaries and it's not unusual to find a complete sub-terminal band on P4 in third generation primaries, where adults have the black markings on P4 confined to the outer web). 
Often the third generation outer primaries are brown hued, another sign of immaturity (but these features don't apply on June LBBG of course: P9 and P10 are full-grown in November). Older birds show more blackish p5-p10 (the age effects the feathers: old feathers are stronger, making the effect of bleaching and wear less obvious).

By June, the old second generation P10 is half a year of age and shows an obvious white shaft, creating a broad white centre in a pale brown feather, on the underside of p10. There is no active moult in the secondaries yet.

Tables:

LBBG 5.412.152 3cy June 12 2005, Amsterdam, the Netherlands. Picture Ruud Altenburg.

LBBG 3cy with arrested moult

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LBBG 3cy H018 June 23 2009, Utrecht, The Netherlands. Picture: Herman Bouman.