Grey Wagtail

A grey wagtail appears in my garden and at my backdoor every winter. It knows I am there, but if I open the door it is off. I have, therefore, no alternative but to take the shot through the thick glass in the door.  On top of that the light usually isn't good and the bird is bobbing up and down. I hope this image doesn't look too bad - it's been processed to within an inch of its life.