| Lesser Black-backed Gull graellsii  NX  sub-adult, May 29 2015, Katwijk, the Netherlands. Picture: Merijn Loeve. Lesser Black-backed Gull, ringed as rooftop breeding sub-adult in municipality Katwijk. Ringed by ringing team Roland-Jan Buijs, see BLOG BUIJS (in Dutch). Black: P4-P10. Mirror: P10. PMS: 0. Small mirror, large dark centres on greater primary coverts and dark centres on secondaries indicate 4CY bird, or retarded 5CY. 
 
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