LBBG adult, June 02 2003, Maasvlakte, the Netherlands.

The lack of black on the bill and the obvious mirror on P10 suggest full adultness. 
In all respects this individual matches the ordinary local Lesser Black-backed Gull, except the moult in the primaries. Early June, only 10% of adult LBBG have started primary moult, with most advanced birds missing P1 and P2. However, this individual is growing P7 & P8 in the right wing and is growing P8 in the left wing. The visible tips of the adjacent feathers are slightly worn, indicating this bird has suspended moult, prior to northbound migration, now continuing this primary moult. In the right wing, P9 & P10 are slightly hued brown, apparently older than P6. Read more about aberrant primary moult strategies in spring adult LBBG on this page, with comments by Peter Stewart.