The breeding range of the White Wagtail (Motacilla alba) circles much of the Northern Hemisphere, extending from southeastern Greenland and Iceland east across Eurasia to Siberia and westernmost Alaska. Through this broad range, there is extensive subspecific variation, with a total of ten subspecies recognized (Mayr and Greenway 1960, Cramp 1988); the form nesting in western Alaska and northeastern Siberia is M. a. ocularis (Swinhoe's White Wagtail).