This Black-headed Gull was marked as pullus on near Sprogo, Korsor, Sjaelland, Denmark (55 20 0 N, 11 0 0 E) on June 5, 2013. It received the ring W[E4XK] on December 24, 2014 in Leiden. In 2019 it was seen in Leiderdorp on August 25, already.