Siberian Grey-headed Wagtail

Wagtail archive see here:

https://radioactiverobins.com/archive/wagtails-eastrn-othr%20white-/british%20yellow%20wagtail%20motacilla%20flava%20flavissima.htm

Siberian Grey-headed Wagtail Motacilla flava plexa

Charles Vaurie, 1959 (The Birds of the Palearctic Fauna, Whitherby,London) and others described the Siberian race of the Grey-headed WagtailM.f.thunbergi as duller and more greyish on the mantle and the colour of the crown grading into the colour of the mantle, less contrasting than in nominate thunbergi as shown in the pictures.

Ahlstrom  & Mild, 2003, however (Pipits & Wagtails of Europe,Asia and North America, Helm,London) found a complete overlap with nominate thunbergi when comparing skins.