Chroicocephalus ridibundus - Black-headed Gull, adult
This Black-headed Gull was ringed as +3CY in København, Denmark (55.43N-012.35E) on March 24, 2009. It was seen in Leiden between January 10 and March 17, 2010. I saw it again regularly between December 4, 2010 and March 12, 2011.