Bob, I'm still just working from a book rather than field knowledge but Olsen & Larsson says of Heuglin's: "Head: in winter (late autumn - March) slightly dark-streaked with coarser dark spots or streaks on hind neck, creating dark necklace. Pattern sometimes includes crown and ear-coverts. Bare parts duller, bill with irregular dark subterminal bar, thus looking three-coloured, but coloration rarely bright. As a result of late moult Heuglin's Gull has winter head and rather fresh white primary tips well into spring when other large gulls have summer head and moderately worn primaries." This bird seems to have quite fresh primaries. Reading back some of Geoff Carey's comments Heuglins would possibly still be moulting its outer primaries at this time. The other option I considered was mongolicus but the large 2nd mirror on P9 isn't visible. I'd wait for an expert to come along! Andrew