Probably an adult female, because the shape of the head is rounded and the facial expression is not as aggressive as in most adult males (see e.g. picture 8). This LBBG is ringed J green 7 black. The exact ring date will be mentioned after contacting the ringer. Most ringed LBBGs were ringed as pulls at the Maasvlakte. Besides this J7, also E780 orange and E920 green were present; both ringed as pullus at the Maasvlakte in summer 1995. 

But gulls from abroad may turn up as well. On April 16 2001, an adult LBBG with a Belgian ring was seen: L 4483. Whether these paler adult LBBGs were born in Belgium or the UK remains uncertain; sometimes adult LBBGs are caught and ringed, so the exact origin in these cases may also be the Maasvlakte.

LBBG adult J7, Missouriweg, Maasvlakte, the Netherlands, May 12 2002.