Chroicocephalus ridibundus - Black-headed Gull
This gull was ringed as pullus on June 23, 2007 near Wisla, Nowe Grochale, Poland (52,43 N, 20,55 E).
This is approximately 35 km NW of Warchaw. It was sighted every winter in the Netherlands.
In October 2007, it was reported from Amsterdam, and in each of the subsequent winters
from Utrecht.