Lesser Black-backed Gull (graellsii & intermedius)

(last update: 09-06-2013)

third calendar year: November - December

The birds shown here are in third winter plumage (3cy). LBBG in 3cy and 4cy can look very much the same in early winter, and particularly when the outer primaries are lost, it may be hard to age many of these sub-adults correctly. Those in 4cy are often recognized by and distinguished from 3cy by the grey outer primary coverts (though with black centres in most cases, as seen in full-adult LBBG as well) and the extensive white tips to the outer primaries and larger mirror on p10 (though this may be sex related and geographical variation . Also, in most cases, the black markings on the bill are less developed in 4cy birds; 4cy LBBG are more adult-like in bare part coloration.
Some photographed sub-adults with rings show the difficulty and variation of sub-adult in the period where the outer primaries are not indicative. See the adult and sub-adult sections.

3cy LBBG normally show some/all of these features:

• Very pale legs and much black on the bill, combined with a pinkish base, which are more adult-like in 4cy (image 1);
• The old coverts are extensively brown bleached and on average adult-grey in 4cy;
• New tertials show a grey base with a white tip which is confined to the inner-web (image 2). Old tertials are either brownish bleached or show a dark brown-black centre and vermiculation on the upper half. In 4cy, the old abraded tertials are all plain normally;
• Scapular coverts may be rather brownish centred, not pure grey as in 4cy and adults (image 3);
• Some of the recently moulted tail-feathers show black isolated spots near the centre (often found in the inner tail-feathers: image 2);
• Primaries show very small white tips in 3cy, especially the outer primaries p6-p10 (image 3). In 4cy these primary tips normally are larger, but this may vary with populations;
• The mirror on p10 is relatively small in size and a mirror on p9 is lacking. 2cy normally don't show a mirror at all and 4cy have the mirror on p10 well-developed. The 3cy p10 mirror is an isolated white spot and normally doesn't reach the feather edge (image 1).
• Primary moult score is high on average (image 1), compared to the more adult-like primary moult score of 4cy. In this respect, 3cy moult strategy is closer to that of 2cy and 4cy is closer to adults. By November, many 3cy have primary moult score of 50, hence all the primaries renewed and fully grown.

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