And here is a view of the upperparts showing fairly typical lesser and median coverts and tail.
Then cut to this bird that was present at Peterhead on Sunday; it is a really stunning thing. In the pics that follow, note how little dark it has in the tail, the very pale underwing and the extensively pale lesser and median coverts. Ive seen presumed GBB x Glaucous hybrids in Newfoundland but they had milky primaries. This bird shows no such signs of hybrid origin and I assume it is 'merley' an extremely frosty GBB. It is a real beauty.