Barn Owl, Little Owl and flava wagtail - Portland Bill and Ferrybridge, 3rd June 2015 © Martin King (the owls) and Pete Hackett (the wagtail)
...the wagtail is quite an oddball: although overall rather anaemic, we presume it's a male and most likely a first-summer (are we just making out paler, old outer greater coverts and flight feathers?), but whatever age it is it's got much more striking wing-bars than you'd expect. It may be just a very freaky Blue-headed Wagtail but if so it shouldn't have such a conspicuous white 'hollow' in the ear-coverts; the latter feature is frequent in the so-called 'Channel Wagtail' which, although many evidently have a paler throat that this, seems like the best bet in this case. Pete reports that the bird called in 'normal' Yellow Wagtail fashion.