Last update of this page: 27-09-05 21:36

General

Nearly every large gull species in second winter exhibits one of the most variable plumages. In this respect, the LBBG is certainly no exception. At Westkapelle, the Netherlands (where most pictures were taken) most present adult LBBG (in late autumn and winter) originate from Scandinavia. Regarding 2^nd winter LBBG, the lack of sufficient individuals with rings makes us rather reserved to the identification on the level of subspecies. As can be read in the captions of the images, a few times we have tried to explain why a particular bird, in our opinion, could be intermedius. However, absence of such presumptions does not necessarily mean that the individual in question belongs to graellsii. Actually, experienced gull-enthusiasts may recognize more birds featuring characteristics of intermedius in this section.

Primary moult stage

The table below represents a primary moult score of November 06 2001 at Maasvlakte, the Netherlands. Throughout the summer months, from May to September, the primary moult scores in 2cy Lesser Black-backed Gulls remained very unpredictable, with much variation, as can be seen most obviously in the July Section. (Compare to e.g. 2cy Yellow-legged Gulls in France). But by early November, only a very small minority has not finished the primary moult (and therefore finish the complete summer moult, with all feathers now at least of second generation).

In the mean time, simultaneous with replacement of the primaries in summer, 2cy Lesser Black-backed Gulls from the Netherlands moult all the scapulars, wing-coverts, tertials and rectrices. In the July and August section the progress of this complete moult is described. By August, the complete moult in the wing-coverts is finished with replacement of the last central greater coverts (normally #6-8) and finally the feathers in the carpal edge (outer lesser coverts). As those last lesser coverts are replaced for second generation feathers, the partial autumn moult starts in 2cy birds only a few weeks after the complete moult during summer, again with the upper tertials and outer median coverts as can be found in several images in the August Section.

Timing and strategy of partial moult

The sequence and extent of this partial moult is quite consistent. The first signs of moult appear in the inner greater & inner median coverts and upper tertials, which are moulted in a  descendant order (from the body towards the wingtip).
The onset of moult in the outer median coverts overlaps with the start of the inner coverts and upper tertials, but on average it starts a few weeks later. Contrary to the inner median coverts, the outer and central median coverts are moulted in ascendant order (from the wingtip towards the body). This explains the old (2^nd generation) 4^th-6^th visible inner median coverts, which are usually moulted in the final stage. The lower lesser coverts follow a less strict schedule and may be moulted 'randomly' as it seems. In the partial wing-covert moult, it is quite common to find birds leaving the inner most greater and median covert out of the sequence, starting with #2.

At the bottom of this page, a table is included to show roughly the stage of partial moult in early November in 2cy Lesser Black-backed Gulls. The exact sequence of the partial moult varies from one individual to another, but most 2cy birds will moult some of the following feathers in autumn: tertials, wing-coverts, scapulars and in a few cases tail-feathers. This was described already in the September section. 

It's hard to label all wing-coverts to exact generation. As can be seen in the May Section, the post-juvenile moult in especially intermedius can be very extensive, even including the tail-feathers. 
By November, the scapulars may have been moulted again to fourth generation feathers, although the pattern is still not completely adult-like. Due to the considerable moult in the scapulars in 1cy birds in August-November, in 2cy birds in April-May (on the wintering grounds), in July and again in September, we exclude the scapulars from further analysis.
Many 1cy Lesser Black-backed Gulls moult the upper tertials and most of the inner wing-coverts to second generation in the post-juvenile moult, either starting on the breeding grounds or in a rapid moult in winter. All wing-coverts and tertials are moulted again in the complete moult in summer. In the partial autumn moult, wing-coverts (at least the inner greater and median coverts) and upper tertials are moulted to thirth generation feathers in most 2cy birds. 

Patterns in 3^th generation coverts

The pattern of the new feathers vary from plain adult-like grey feathers to feathers hardly distinguishable from the old second generation feathers. Those feathers show a anchor pattern or barred pattern (dark brown to blackish) with a pronounced dark broad shaft-streak on a warm brown base (but the brown tone of these feathers will bleach to almost white with time). Some birds have an intermediate coloration: a plain grey base of the feather with a brownish upper half, an anchor pattern and a clear white fringe. 
Some  birds may look very advanced, almost similar to 3cy birds, after completion of the partial moult, with plain grey feathers in all the scapulars, the upper four tertials, the inner 10 or so greater coverts, all median and lower lesser coverts and all visible lesser coverts. In general: almost all grey upper-parts in these birds.

As in the October Section, 2cy Lesser Black-backed Gulls can be divided in three categories:

1. As can be read in the captions, some individuals look more 'advanced' in the moult of the upper-parts and wing-coverts. Actually, those 'advanced individuals' don't necessarily show an 'advanced moult stage' but rather show an 'advanced pattern on the feathers'. Quite some birds show a complete or almost complete greyish scapular and mantle region, a complete greyish median covert bar, combined with greyish inner greater coverts and single greyish tertials. On a whole, this gives a pretty 2^nd summer-like appearance. Click here for examples of this group. From November onwards, over 90% of the 2cy LBBGs present at the Maasvlakte and Westkapelle show at least new inner greater and median coverts, with many (>60%) showing new central median coverts or completely new median coverts.

2. The exact same moult stage (i.e. amount of moulted feathers to 3^rd generation) can be found in very brownish or variegated birds as well. Regardless their same moult stage, the look more 'immature, second generation-like', an impression created by the anchor or barred pattern on the new 3^rd generation feathers. It's the brown impression that gives these birds a less advanced look, but the actually moult timing is average. This partial autumn moult of e.g. median coverts has not been found in 3cy LBBG, seen at the same place and date.

3. The intermediate birds show a grey scapular region combined with patterned wing-coverts.

So far, we didn't find criteria to allocate these categories to sexes or geographical locations. Probably, "advanced looking individuals" can be found in any populations, though there is a slight tendency to name the "less advanced birds" from category 2 British graellsii as they often stand out as robust and strong individuals, unlike the average compact, smaller Scandinavian intermedius.

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