You might have seen this heavily debatted Motacilla from Sweden (still present)? Suggestions are either, an unusuall looking Citrine (as you can see), or a hybrid or even a Yellow. The head pattern - with non pale surroundings to the earcoverts as well as the huge pale forehead patch, and not the least, clear pale bill base confuses.
A lot of birders has offered their thought on this peculiar Motacilla, one being Krister Mild, who suggested that the bird is not a Yellow Wagtail and apart from the yellowis bill base he thinks that it might well be a Citrine, the main problem being the bill base colour. Some 1cy Citrine do lack the pale surrounding to the ear coverts. The seemingly narrow wingbars for a Citrine might simply be due to wear.