Chroicocephalus ridibundus - Black-headed Gull, adult
On December 28, 2009, i.e. three days before my first sighting in Leiden, this bird was
ringed at the Oosterpark (52.21N, 04.55E) in Amsterdam, 37 km away from Leiden.
In October 2010 it was reported dead, found hanging in a tree near Berlare, Belgium.