Myself and my photographer friend, Dinis Cortes, found this interesting gull at Ferragudo near Portimão, Algarve, Portugal on 18th January.
According to the Helm Gulls guide (K.M.Olsen and H.Larsson) this bird fits in with this hybrid, "frequent in Greenland". There are 4 GBB Gulls in the area at the moment, and this bird certainly attracted my attention and looked "Glaucous-like" in flight - very ghostly. It would be nice to receive opinions!
Photos by Dinis Cortes