Peter Adriaens (Belgium)
Ies Meulmeester (Netherlands)
Larus argentatus sensu lato 4P24 adult, May 05 2014, Zastów Karczmiski, Poland. Picture: Łukasz Bednarz ringing team.
Location: Zastów Karczmiski, Poland - colony at the banks of the Middle Vistula river.
Middle Vistule river is a location where several taxa breed: see composition. Since this is a mixed breeding population where hybridisation is not uncommon, the ringing centre in Poland decided to label birds "Larus argentatus sensu lato". Still bulk of the breeding birds in Middle Vistula region show features of cachinnans.
Breeding bird trapped at the nest, showing little similarity to argentatus (F2?) in obvious gonys, pink legs and medium sized medial band (no deep tongue on P10). All these features can be found in cachinnans as well however.