Mystery Wader

I received this from one of my regular readers who says, "I attach a couple of pictures I took of a small wader last May on the Tongue Barrier on the north coast of Scotland. It was with, and pretty much the same size and shape as Dunlins, but appears to be in a transitory colour scheme. It is clearly a calidrid, my best guess is a Stint, but precisely which one? I would value an opinion."