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, 2nd & 3rd photo: Histria area, Constanta County, Romania, 21 May 2018
4th photo: Mila 23 area, Danube Delta, Romania, 24 May 2018
5th photo: A juvenile. Babadag Forest, Babadag, Constanta County, Romania, 22 May 2018