I didn't realise that pied referred to a specific subspecies, I thought they were just alternative names. Thanks for the information
The Pied Wagtail (Motacilla alba yarrellii) is restricted to Great Britain and Ireland, with some individuals in the north of Scotland wintering in Spain but all other populations remaining resident - it is noticeably darker in colouration when compared with other subspecies. The taxon found in more or less the entire remainder of Europe is the nominate subspecies, which is the taxon most often called White Wagtail - this subspecies occasionally pops up in the British Isles as a vagrant, and as noted above the two taxa can be found together in Spain during the winter months, but otherwise the ranges are quite separate
