Lesser Black-backed Gull (graellsii & intermedius)

(last update: 21-2-2011)

second calendar year: June

First summer (2cy) LBBG can be classified in 3 categories. In the 2cy LBBG May section, we give details about this classification, based on research done last years. Of course, the classification for May applies to June as well. In year 2001, we tried to get more information about the extremes of these classes, especially regarding moult strategy and moult pace.

First type LBBG (local typical 2cy) in June:

The under-parts and head are patterned with bold markings on a dirty base. The partial spring moult involves head and under-parts. By June, birds show neat streaking on head feathers, combined with abraded under-parts (often the vent and flanks).

The scapulars may have been moulted last autumn (as early as September) to anchor patterned second generation feathers. By June, these may be replaced again and the new pattern is largely unpredictable. They may appear adult-like grey or brown-grey, often with a pronounced dark shaft. But the third generation feathers may also show an almost similar pattern as the second generation feathers, again with anchors or barring. 
Some birds may require their first renewed  second generation coverts as late as June. Fresh feathers can be recognized by the white fringe. The juvenile wing-coverts are shed rapidly and new second generation coverts start growing. In some individuals, complete covert-rows have  been shed and the new feathers grow simultaneously. Again, the pattern shows barring or anchors. If the coverts were not moulted on the wintering ground, moult starts with the median covert row, combined by a few inner greater coverts and randomly some lesser coverts (though often in the inner part of the lessers). Normally, this first type LBBG has some remaining juvenile coverts in the carpal edge (outer lesser coverts).

The tail is still largely black-brown and the present rectrices are nearly always juvenile, though central rectrices are shed now.

The bill is mostly blackish with only a slightly paler base. Legs are pink.

All 2cy LBBG show active primary-moult in the inner primaries in the first week of June. On average, towards the end of the month, P4 is growing and P6 is shed.

Second & third type LBBG in June:

These types show a short neck, small rounded head, fine and short bill, short legs (especially tibia) creating a delicate and compact appearance, in some individuals pronounced by the relatively short primary-projection. Also, plumage and timing of moult in wing-coverts and tail-feathers on average are different from the first type. The first type LBBG start moulting coverts and scapulars at a high pace and especially the primary moult may be more advanced than in the second and third type.

We treat the second and third type together, because in June the differences between these two become less obvious as under-parts become white and the exact pattern of scapulars and coverts is hard to detect on the abraded feathers. As said in the 2cy LBBG May Section, these types already replace scapulars and many wing coverts on the wintering grounds. By June, the pattern gets lost and the fringes get worn. 2cy LBBG belonging to these types start growing third generation coverts now. As mentioned before, third generation coverts may resemble second generation coverts in pattern. Here, in these two types, the third generation coverts are often adult-like plain dark-grey (sometimes with an all-black central wedge), unlike the bared or anchored 2^nd generation feathers.

Tail-feather moult

The number of moulted rectrices in the winter-quarters is highly variable and subsequently we find large variation in June. Advanced individuals show a complete second generation tail, while others return in a clearly suspended moult-stage. In the winter-quarters, many individuals do not proceed the moult of the rectrices in a descendant sequence, since migrating birds in spring really show every conceivable moult-stage (e.g. R5-6 second generation, while R1-4 are still juvenile, etc).
Some birds do not show fully-grown rectrices, but it is at least not usual to find a tail in active moult by May and early June. Apart from the obvious fresh white tips, the pattern of the second generation rectrices is mostly juvenile-like, but the darker parts are pure black and the pattern is more vermiculated. However, birds with for example a partially white R2, a nearly complete black R3 and with a R4 showing much white, are common. A small minority shows only very little black on the second generation tail-feathers.
The renewed upper-tail coverts are complete white or with some sparse black barring on a white base.

Wing-covert moult

The wing-covert moult has mainly been suspended prior to migration, with in most cases a generation contrast between the inner and outer coverts. This especially applies to the greater coverts, which often show a mix of juvenile and 2^nd generation coverts, where tertials and median coverts are often already renewed. The moult-stage of lesser coverts is more advanced than the greater coverts, but especially 'upper' lesser coverts are less advanced than the tertials and median coverts. Once returned, many birds start shedding complete covert bars and grow new feathers simultaneously. 

Primary moult

The onset of the primary moult in second and third type 2cy LBBGs in early summer is on average slightly later (1-2 weeks) than in typical first types. Additionally, the individual variation is more pronounced, with e.g. in the third week of June, birds with only P1-2 missing and birds which already shed P7. However, in comparison with the first type, differences in timing of primary moult is usually not significant.

Tables

Lesser Black-backed Gull 2cy N031118 June-August 2012, Boulogne sur mer, NW France. Picture: Jean-Michel Sauvage.