Images of a 4th-calendar year type European Herring Gull Larus argentatus argenteus, ringed on 2 June 2014 as Green Y.BPS in the gull colony of IJmuiden (Forteiland), the Netherlands. It was caught on the nest while breeding.
Aging it as a 4th calendar year was done based on the brown coverts, the adult looking primaries and the presence of the markings in the tail.
Measurements that were taken indicate that this is a male.
I find it fascinating that gulls of this age are chosen by adults to start a bond and to actively take part in the breeding process, despite the immature plumage features. Does this indicate that pair bonding is all to do with postures and vocalisation, or does it mean that there is a shortage of adult males?