Eleven subspecies of the White Wagtail (Motacilla alba) are currently recognised and they all have slightly different plumages.
This is Motacilla alba alba, the nominate subspecies of the White Wagtail which occurs on the European continent and migrates down as far as Kenya.

1st photo: Herdla, Hordaland, Norway, 21 August 2014
2nd photo: Oslo, Norway, 24 August 2014
3rd photo: Eidfjord, Hordaland, Norway, 22 August 2014