Wagtails were once a common sight in my garden. I even got the occasional Grey as well as the usual Pieds. I cannot remember the last time I had either and even a visit up town fails to produce a sighting where once they were everywhere.
I have just checked the BTO GBW stats for the first three months of 2014 which shows records of PWs nearly 50% down compared with the same period last year. I don't know if alarm bells are ringing anywhere yet but perhaps they should be.