Photo 10: LBBG graellsii sub-adult, June 17 2001, Naaktstrand Maasvlakte, the Netherlands. 

Occasionally, very slate grey individuals turn up. They often show remarkable fresh large tips on the primaries and often extensive streaking, especially around the eye, on the nape and on the crown. Note the extra-ordinary large white mirror on p10, totally unlike the immature local and Scandinavian LBBGs.

Maybe they originate from the UK, Faeroes, Belgium or maybe further south. They are believed to belong to the true, 'English' graellsii, and do not represent local Dutch intergrades. Remarkably, these individuals often show very large fresh primary tips (note the extensive white tip, merging with the mirror on p10) and often there is (faint but apparent) streaking on the head, as in winter plumage.
Here, the iris is blue-yellow, the legs are pale pink-yellow and the pale yellow bill has a broad obvious band and is the prime clue to age it as a sub-adult.
The outermost greater coverts have been shed (exposing the secondaries, which seem to be adult-like) and new plain grey adult-like coverts are growing. The tail is all white. In general these birds give a neat impression, showing no obvious wear on the feather fringes. Maybe, winter was spend on inland locations on northern latitudes, so the feathers have not been exposed to severe weather conditions.