photo 9741: Lesser Black-backed Gull graellsii E303 9cy, April 06 2003, Missouriweg, Maasvlakte, the Netherlands (51.59N,04.02E). 

Most probable an adult female ringed, left orange E303, ringed July 08 1995. Note the friendly facial expression and the elegant bill, indicating its a female. Although already in 9cy, there is still some black on the bill in this bird by early April. Note the relatively small white tips and the lack of a mirror on P9, while P10 shows only a small mirror. There seems to be a contrast in brown hue between P8 and P9.