Adult European Herring Gull with immature central tail feathers Green Y.BRD – 20140602

This adult European Herring Gull Larus argentatus argenteus was caught while breeding in the gull colony of IJmuiden (Forteiland), the Netherlands, on 2 June 2014 and ringed as Green Y.BRD.

It surprised us by showing immature markings in the central tail feathers while showing no other markings of immaturity (no dark markings on the coverts or alula or black markings on the bill).

Interestingly, the markings appear on adjacent webs: the outer web on the one feather and the inner web on the other.

Its exact age is unknown but it is likely to be in its 5th calendar year.







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