Lesser Black-backed Gull (graellsii & intermedius)

(last update: May 17 2015)

Lesser Black-backed Gull graellsii HR 3CY, June 29 2017, Utrecht, the Netherlands.

Green tibia HR & black tibia, and metal Arnhem NLA 5.508.103. Ringed as pullus on June 28 2015, at Europoort (Dintelhaven), the Netherlands (157.00 N 406.00 E), by ringer Hans Keijser.

Recoveries:
29-6-2017 Utrecht (Papendorp), Utrecht, NL 5.204,00 N 505,00 E colourring read Mars Muusse

Before ringing data were received for this individual, green HR was labeled "retarded 4CY June bird". The obvious white tipped central primaries and the obvious mirror on P10 pointed to 3rd generation primaries, and as could be expected for any 4CY LBBG in spring, these primaries are pretty worn by June.
But the assumed age of this individual proofed to be incorrect! By June 2017, green HR is in fact still 3CY. Are the primaries really 3rd gen or can 2nd gen P10 show such an obvious mirror too?
Or is this bird extremely advanced due to a rapid extra moult last winter, pretty early in winter, to get this wear in the primaries by June? How old is that tail? How old are these secondaries?