possible hybrid LBBG x YLG E494, September 20 2003, IJmuiden, the Netherlands (52°27'0''N, 4°33'0''E)

An adult with a red darvic ring, ringed in IJmuiden summer 2001, probably as adult or near-adult. Red darvics E481-E499 were used for yellow-legged gulls (michahellis) or hybrid Lesser Black-backed Gull x Yellow-legged Gull (graellsii x michahellis). In E494, upper-part coloration and moult scores very much indicate local Lesser Black-backed Gulls (so-called 'Dutch intergrades'). 

On September 09 2003, P8-P10 were still old (P5 fully grown), on September 20 2003, P9-P10 are still old (P6 fully grown). , and P4 fully grown. In general, by the time P6 reached the length of P5, adult birds start to drop the central tail-feathers. In the image below, the tail obviously lacks several feathers, when P6 exceeds P5. Moult of the secondaries started as well, with birds first dropping the outermost secondary (S1, at the division with the primaries). Moult progresses as a wave through the secondary bar towards the body, with old feathers ahead and leaving new feathers behind.