Lesser Black-backed Gull (graellsii & intermedius)

(last update: 20-2-2011)

second calendar year: July 

The classification between the three types, as set up in the May and June section, is hard to maintain now moult in all feather groups is going on. Extreme differences may occur in all types. In the general section we describe the extremes as seen in July.

Remiges moult:

The average primary moult score for mid-July is about 25. On average, p7-p10 are still juvenile outer primaries, p4 is the latest full-grown second generation primary, while p5 and p6 are growing. The extremes found in year 2001: 

A: Delayed moult with only p1 and p2 shed, no new primaries growing (photo 20). The primary moult score is only 2. 

B: Most advanced moult by mid-July includes only p10 and p9 still juvenile and p7 already longer than p6, which is full-grown (photo 22). Moult score is 36 here. 
Such tremendous extremes in primary moult pace can probably only be found in the LBBG-complex; none of the other large white-headed gulls in Western Europe share this phenomenon. 

Some odd primary moult strategies may appear as well, e.g. growing p4 while p5 is still not shed (image 9 and 10). Normally, when a new growing p4 is over half of its final length, the next primary (p5) has been dropped, and, not uncommon, p6 as well. Actually, p4 at 50% and p5 still present may be an indication for arresting the primary moult, but there seems to be no good reason for such a moult strategy in July.

By the end of July, the first secondaries are shed. In many cases, the outer group of approximately 4 are shed (S1-4), then a small block of secondaries remain (app. S5-S9) and the inner secondaries (S10~S17) are shed as well, although often a few remain in the inner-arm (app. S15-S16). The secondary moult strategy resembles the strategy of 2cy michahellis in this respect, with the bulk of LBBG being later (August) in the moult of secondaries.

Rectrices moult:

As could be seen in the May Section, some 2cy LBBG had replaced the entire tail by May. This, of course is the early extreme, only shown by the vanguard of 2cy LBBG. Normally, July is the month where 2cy LBBG shows an incomplete tail. But still, all rectrices may be juvenile as well (as can be seen in image 14).

Scapulars and Wing-Coverts:

As can be seen in almost all the pictures, moult is in progress in both the scapulars and wing-coverts. Some advanced individuals have replaced the entire greater covert bar (image 6 and 24), but normally the central greater coverts are missing or still growing. The outer greater coverts are replaced inwards, after outwards moult of the inner (3-5) greater coverts and the two meet at greater covert #8 approximately. By July, the complete median covert bar has normally been replaced and the moult of the lesser coverts is taking place more randomly. The under-wing coverts probably follow the same sequence as the upper-wing coverts. The pattern on second generation under-wing coverts is more contrasting black-white than the old juvenile variegated brownish under-wing coverts. See e.g. image 19.

On average, the tertial moult is in progress, with the upper two tertials missing or growing in most 2cy LBBG (see e.g. image 10 for an individual with average moult pattern by early July).

By July, it is very difficult to be certain of the exact age of some scapulars. As could be seen in the September section of 1cy birds, many individuals moult scapulars to second generation feathers by late summer. By May, 2cy LBBG may show fresh scapulars again and it's hard to exclude that some individuals by then already have third generation, adult-like scapulars. And now again, by July, almost all 2cy LBBG show at least several fresh, recently replaced scapulars of which some may be of fourth generation. It's expected that these 4^th generation feathers appear very adult-like and indeed some individuals show abraded plain grey-brown scapulars combined with fresh adult-like feathers. It has to be said that ageing such scapulars is very hard and as long as (at least some) juvenile scapulars appear, fresh scapulars may be only second generation feathers (replaced very late).

Intermedius types:

By July, the majority of the local Dutch 2cy can be found in the Netherlands and this seems to be the period that many passage intermedius migrate north. Going through a group of 2cy LBBG in July (see image 1, 2 & 3), some individuals appear long-winged, short-legged and generally are more elongated than the average local Dutch 2cy LBBGs. In the captions these birds are mentioned "probable intermedius" as we presume these to originate from Scandinavian populations. Regarding moult pace and moult sequence, there is much overlap with the local Dutch LBBGs.