Lesser Black-backed Gull (graellsii & intermedius)

(last update: 09-06-2017)

third calendar year: August

In 3cy LBBG many wing-coverts and the uinner primaries are replaced now. There is a large difference between the start and the end of August. Plumage changes into fresh adult-like upper-parts and under-parts. Wing coverts and tertials become (at least) third generation and mantle and scapulars become fourth or even fifth generation, after the moult to third winter plumage. From head to toe you can see the following changes.

• The bill becomes paler. Variation in bill colour is low. Bills with a black base (present in 9%, n= 100) are rare while some advanced birds (17%) show an adult-like bill. On average, birds show an adult bill with a dark smudge on the upper mandible (74%).
• The iris turns pale yellow, but a white or darker peppered iris occur.
• The head varies from all-white without any speckling (old, worn, 15%), finely streaked from crown to neck (65%) to new heavily streaked (20%). Birds actively moulting the head-feathers look spiky.
• The under-parts are actively moulted into white feathers. Nearly 100% of the birds shows all-white under-parts, a few have streaking in the hind-neck.
• By the end of August, all 3cy LBBGs show adult grey upper-parts.
• Many to nearly all 3cy LBBGs have finished moult of mantle and scapulars (by September all birds). The upper-parts resemble adults now (being fourth or fifth generation).
• Tertials on 3cy LBBGs in August can exist of old 2^nd generation (at least) feathers or newly moulted 3^rd generation feathers. The difference is obvious: the new tertials resemble adults, contrary to the blackish centred old tertials. About 50% of 3cy LBBGs have all tertials new, with new upper tertials and old lower tertials being second best.
• The wing-coverts are in active moult, so a gap in the covert bars is very common. The moult starts with the medians. When median covert moult is halfway, birds start moulting the greater and lesser coverts as well, normally starting with inner and outer greaters. Last moulted feathers are the outer lessers.
• Common moult-state in 3cy LBBGs by late August is:
  new inner and central medians (third generation), 4 new inner greaters (third generation), missing the central greaters and growing the outer-half inwards and 50% of the lessers old. The third generation coverts normally are adult-grey without barring.
• Primaries are moulted outwards, the primary-score by the end of August averages 34 (n = 26), all birds showing fully grown p4 at least (see table). Third generation primaries are very adult-like but p10 often shows an obvious smaller mirror. (Later in the year, bleaching gives a browner tinge on the primaries than on adults.)
• Secondaries are dropped inwards, from the moment p5 or p6 is halfway grown, creating a gap from p1 inwards. Only a very few 3cy show secondary-moult in August. No or nearly none 3cy show fully 3^rd generation secondaries by the end of August.
• The under-wing becomes paler, under-wing coverts are replaced by adult-like feathers. The under-wing coverts are probably moulted in the same sequence as the upper-wing coverts.
• The tail is old, second generation on many birds (60%), in active moult (20%) and fully grown third generation, white or with very restricted black markings (20%). Old worn tail-feathers occur as some 3cy and 4cy LBBGs may moult the tail on the wintering grounds, subsequently returning with a new tail in spring.
• Leg colour varies from pink to (pale) yellow.
• Birds with advanced mantle and scapulars already look exactly like 4cy birds as they return by May in the Netherlands.

Tables

LBBG 3cy Belgium: graellsii / Dutch intergrade

LBBG 3cy the Netherlands: graellsii / Dutch intergrade