Pair of Grey Wagtails, the male (top and right) with the stronger yellow chest and rump and the female with a paler lemon yellow; both with grey head and back.
The male (above) has a dark chin in the breeding season (and white when non-breeding).
Male with fly
Grey Wagtails can be easily confused with Yellow and Citrine Wagtails (which have more yellow on their belly, no white flank, and sometimes yellow face/head/chin, and the former an olive-yellow back).
The female Grey Wagtail (above) has a white chin all year.
Female Grey Wagtail
She also has a paler yellow chest and rump than the male.
Walking on water-lily leaves is typical of all wagtails in the hunt for aquatic insects.
The juvenile Grey Wagtail (above) has no, or very little, yellow on its chest and is easier to confuse with juvenile Yellow/Citrine/Blue-headed and even White/Pied Wagtails.