Isabel: dilution mutant Herring Gull at Seafield again

I spent a couple of hours checking the gulls at Seafield today. While it was the Lesser Black-backed Gulls that predominated on St Margaret's Loch en route, at Seafield it was almost entirely Herring Gulls at the recycling centre. The isabel dilution mutant was the clear highlight in among the latter. It showed on three occasions and posed well on the ground as well as in flight. Very nice, thank you - I had hoped for better views and was not disappointed.

Interesting that it appears to already have dropped a couple of innermost primaries. Could this early moult may be a result of the fragility of the unpigmented feathers?