VAN DER LEIJ RJ (2017) Individual recognition of Caspian Gulls Larus cachinnans. LIMOSA 90 (2): 77-83.

In the winters of 2010/11 to 2015/2016, Caspian Gulls were observed and photographed at Lake Pikmeer, in the Dutch province of Fryslân. Photographic documentation of every Caspian Gulls, including flight shots, allowed individual recognition. In this note I describe characteristics that can be used to distinguish individual Caspian Gulls from each other. For young birds (first to third winter plumage) markings on the tail are very useful, whereas for older birds (third to adult winter plumage) markings of the outer primaries are more important. By identifying individual Caspian Gulls on the basis of detailed pictures a better idea about the true number of individuals visiting a certain site can be obtained. The maximum number of Caspian Gulls observed at Lake Pikmeer in 2015/16 was eight, whereas 16 different individuals could be distinguished from the pictures.

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