This was on my want to photograph list on this trip up to the Orkney's. It is quite easy to miss or overlook. A classic LBJ, a little brown job, a name given to a bird that flits past you, or darts into a bush. You don't get a good view, or you can't see any distinctive features that would identify it instantly.
These have white flashes under the edges of their tails, but otherwise nothing really special to draw your attention. They are commoner than you might think, but often not seen for what they are.
Closely related to the better known Linnet, this is a Twite.
