Lesser Black-backed Gull (graellsii & intermedius)

(last update: May 17 2015)

LBBG 3cy, May 27 2003, Missouriweg - Maasvlakte, the Netherlands. 

This bird has moulted most of the upper-parts, prior to northbound migration. Almost all inner wing-coverts were included as well and many still look relatively fresh, compared to the (10 months) older wing-coverts in the carpal edge. Some brown hued greater and inner lower lesser coverts are more abraded and were probably moulted in the partial autumn moult as 2cy, now 1/2 year old third generation feathers. All scapulars have been replaced for grey adult-like feathers, but a few brown hued older feathers can be seen in the rear scapulars. The tertials are grey as well, the lower tertials with a broad white tip. The fringes of the upper tertials are slightly worn. Soft parts acquired adult-like pigmentation with the bill showing a small black bill-band and bright red on the gonys. The legs are already yellow. The complete tail has been renewed to at least third generation as well, as all the rectrices are plain white. Primary moult has been started in early spring (probably February) in this individual and still continues: P8 is still growing third generation and P9-P10 are old second generation. Not surprising, most of the secondaries are moulted as well, with the brand-new white tips of the secondaries just visible beneath the central greater coverts. As can be seen in the image, the innermost secondaries (about #16-18) have a brown centre and an abraded white tip; i.e. they are old second generation. Note the head-moult, creating a 'moth-eaten' appearance.

LBBG from the Netherlands ("Dutch intergrades") and from Scandinavia (intermedius) are sometimes considered to show a similar moult strategy as Herring Gull (L. Argentatus argenteus). Herring Gull moult the head, partly the body, scapulars and mantle to second generation in 1cy autumn. Next moult is the replacement of body and head in spring in 2y. By summer, the complete plumage has to be renewed, so a complete moult takes place. From then on, a partial moult includes head and body in spring and includes all feathers in the complete moult in summer.

This however is a too simplified picture, for both LBBG and Herring Gull. Graellsii and intermedius LBBG may show a contracted moult scheme, as can be found commonly in the eastern counterpart of the taxon fuscus. The 2cy May section already shows several birds in 2cy with new tail-feathers in spring in NW Europe (here, here, here & here). The literature ascribes tail-feather moult as restricted to the complete moult (in summer). But tail-feathers can be renewed on the wintering grounds in early spring (February). The tail is then completely renewed in summer in the complete moult (see August Section), and may appear advanced compared to birds with second generation tail-feathers. By October, 2cy LBBG can be found with missing central tail-feathers again (here). And on the wintering grounds, 3cy February birds may moult the tail-feathers as well, just as in some 2cy birds (here & here). By spring, when they return in NW Europe, some 3cy LBBG show a complete white tail (e.g. the bird on this page).

As is the case with the tail-feathers, some West-European LBBG follow a contracted moult in the primaries as well. In the Netherlands, this is most easy established in 3cy and 4cy birds, and this is exactly what we find in the field. However, people in a position to examine birds in the hand (e.g. ringer Peter Stewart) do find this phenomenon in adult LBBG as well.
The individual depicted here is a nice example, with the primary moult started early in spring (probably February) before returning to NW Europe. Normally the moult gap is closed before migration is initiated, as migrating with a moult gap seems reasonably inefficient. However, some individuals don't seem to bother too much about a small gap and return with still growing primaries (also this intermedius).