Lesser Black-backed Gull (graellsii & intermedius)

(last update: May 17 2015)

LBBG adult, August 22 2012, Katwijk, the Netherlands.

P1-P10 old.

By the end of August, most LBBG have started primary moult in the Netherlands. However, it is still possible to find adult LBBG of the taxa graellsii and intermedius, which have still all primaries, P1-10 old, even in the first week of September.

By September, such birds with 10 old primaries and a snowy white head may be misinterpreted for nominate fuscus, which often has all primaries still old by early September. But intermedius often show a paler shade of grey in the upper-parts and colder brown worn scapulars and coverts.

LBBG with 10 old primaries by late August are not numerous and in large scale surveys at Maasvlakte (near Rotterdam) we estimate < 3% of adult LBBG to have 10 old primaries (n = 519 on August 28 2001, n = 361 on August 22 2002). But it seems quite reasonable to presume that adults which are late in primary moult, may have a stronger tendency to first migrate south and start moult after arrival at the wintering grounds. Research of migrating adult LBBG along the Atlantic coast would be necessary to answer this question.