birding never sleeps: Arctic argentatus on the Adur (10 December)?

Saturday 10 December. Having worked five days in a row for the first (and only!) time this year I was very keen to get out, but a poor forecast wasn't encouraging and I didn't go further than Goring Gap. Sadly no sign of the Snow Bunting but Mediterranean Gull is usually a safe bet and there were 7 adults in the fields along with 335 Dunlin, 85 Ringed Plover and 11 Sky Larks with 41 Sanderling on the beach. Coming back to Shoreham I called in at the Yacht Club near the Fort and on the small beach there a Herring Gull type showing strikingly little black in the closed wing caught my eye. I took loads of photos, some of it stretching, but nothing useful when it flew off towards the Lifeboat Station. Two Purple Sandpipers were roosting below the wooden jetty despite the tide being halfway out. On the Adur were three colour-ringed Herring Gulls, one local and two North Thames birds. Later I returned with Megan but this time couldn't find anything amongst the gulls. In contrast to Goring Gap I've not seen a Med gull on the Adur for a while.

one of seven adult Mediterranean gulls in the fields at Goring Gap, always nice to see

striking Herring Gull at Shoreham Yacht Club

its mantle appeared a similar colour to the bird behind but perhaps darker than the back bird

but it showed very little black in the closed wing suggesting argentatus

although it wasn't particularly large

extensive white tip to p10 is also indicative of argentatus

at this angle the black in the primaries hardly shows at all

making the wings look more like a Thayer's Gull's

when it stretched it showed an almost complete lack of black on all but p9-10, closest to plate 369 of Olsen and Larsson's Gull book (ssp argentatus of arctic type, note restricted amount of black in wing-tip compared to 'southern' argentatus