first-winter flavas

clearly need to do some swatting on these-- up to 15 on a local field of late with a large range of variations from full adult yellow, males to this grey bird with yellow restricted to undertail coverts; had one this morning with brownish toned uppers, whitish super and underparts down to yellow vent and undertail coverts -- also a strong call heard from an unseen bird but not recorded in the rain -- need to get back if it fines up later -- rubbish heavily cropped shots here

Blue-headed Wagtail

a striking flava with the Yellow on the local patch -- the head pattern seems good for flava as does the upperpart colour and the striking call also sounds good so on consideration I think it is a good Blue-headed particularly having seen a typical lavender headed channel wagtail a couple of days later

flava wagtails

the upper three images appear to be a nominate flava but can a hybrid be ruled out? and what of the bottom two?