Fortunately Salva Garcia has been visiting the pre-roost flock of Lesser Black-backed Gulls at Malaga Port, Spain for many winters, and he regularly reports Guernsey colour-ringed Lesser Black-backed Gulls from this site. In 2011 I was fortunate enough to join Salva and Gabriel Martin on one of their weekend visits to the port. It was a memorable experience! What makes this site so dramatic is the high concentration of LBBGs in a relatively confined area. The gulls do not roost in the harbour, but gather from mid-late afternoon before flying out to sea to roost. This weekend Salva sent the photo below, along with another seven records of Guernsey cr LBBGs - my thanks to Salva for all his hard work in the area!
LBBGs at Malaga Port (c) Salva Garcia
LBBG White 7.Z4 (from Sark) at Malaga 24 November 2013 (c) Salva Garcia