Partnerruil bij Zilvermeeuwen Larus argentatus in IJmuiden

This note describes how a nine year old, apparently experienced and in 2008 certainly successfully breeding male Herring Gull, colour-ringed Y.AAH in 2008, broke up with its partner (colour-ringed Y.AAC in 2008) in the next breeding season (after having been seen together in the pre-breeding phase), and bred successfully again with another (unringed) female in 2009. At least one chick successfully fledged in either season (Y.ACU in 2008, Y.ALK in 2009). The partner (Y.AAC) was eventually relocated in 2009, together with an unringed partner, but it is unclear if this bird did nest again in 2009.