The Black-headed Wagtail is one of the Central Asian subspecies of the Yellow Wagtail; this subspecies, from southeast Kazakhstan, is sometimes called the Turkestan Black-headed Wagtail.
Only the male has the bright yellow front and black head; his back is olive and grey like the nominal Yellow Wagtail, his chin is white.
The bright yellow front and white chin
Fighting for territory but the action is too quick for the camera
The female Black-headed Wagtail doesn't have a black head. She has a grey head and back, less rich olive than the male and her front is pale off-white and yellow.
She also has the hint of a white eyebrow.