As I passed the alfalfa patch this beautifully plumaged Black Headed Wagtail showed itself. I've narrowed the subspecies to Motacilla feldegg ssp. superciliaris but yellow wagtails have an enormous number of forms and intergrades and this makes identifying them a real challenge.
This shot shows the sharp border between the black neck and paler mantle.
One of the many Black Redstarts.