Citrine Wagtail

I've seen one citrine wagtail in the Central Range of Karizanga NP in Assam (northeastern), India. The term citrine refers to its yellow coloration and wagtail refers to its characteristic tail pumping behavior. Males in breeding plumage are gray or black above, with white on the remiges, yellow below (possibly diluted by white), and on the head, except for the black nape. In winter plumage the yellow underparts may be diluted by white and the head is brownish with a yellowish supercilium. Females look like washed-out versions of males in winter plumage. 

Based on the illustrations below, it looks like this is a female in between breeding and non-breeding plumage in ssp. citreola. 

Illustration of non-breeding female ssp. citreola from Birds of the World. 

Illustration of breeding female, ssp. citreola, from Birds of the World. 

Illustration of male ssp. citreola from Birds of the World. 

Range from Birds of the World. 

Subspecies citreola is found from Finland and northern Russia, east to central Siberia, Transbaikalia, Mongolia and northeastern china and winters mainly in the Indian Subcontinent and Southeast Asia.