Albert de Jong
Larus cachinnans 1CY XXEN September & November 2014, the Netherlands. Picture: Edwin Kerssens & Jacob Jan de Vries.
Data pending, probably ringed as pullus in Oberspreewald-Lausitz, Brandenburg, Germany (51°42'00"N 014°06'00"E). This is 100 km SE of Berlin and Lausitz holds a mixed colony in the lake. At this location ringing takes place in colonies of mixed species, with Herring, Caspian and Yellow-legged Gull, so identification is not always straight forward. The possibility that juveniles are not a pure bird is therefore not unlikely.
This green XXEN seems to be cachinnans, albeit with 'spread out' streaking on head (you would prefer it concentrated in the hindneck; overall streaking is more like in Herring Gulls).
below: Larus cachinnans 1CY XXEN September 14 2014, IJmuiden, the Netherlands. Picture: Edwin Kerssens.
Lower scapulars still juvenile. Coverts and tertials also juvenile.
below: Larus cachinnans 1CY XXEN November 18 2014, Terschelling, the Netherlands. Picture: Jacob Jan de Vries.
Coverts and tertials juvenile.