This is only the second report of a British-ringed Black-headed Gull in Switzerland, following a bird ringed as a chick in Essex in 1999 and seen in December that year. The map below shows all movements of Black-headed Gulls to/from Britain & Ireland, from the Online Ringing Report.
Franck has a bit of a track record finding North Thames Gull Group birds: in April/May 2014 he reported a Yellow-legged Gull (Orange YY5T) originally ringed at Rainham Tip in February 2014. This bird also has an interesting history, being seen just five days after ringing in France, before moving on to Switzerland.
|Wanderings of Orange YY5T|
|Orange YY5T at Pitsea Landfill on 29th November (c) Richard Bonser|