While video-ing a spur-winged lapwing for the purposes of this study on blinking, it showed an unexpected behaviour.
As it was pecking at the mud, it paused repeatedly to tap the ground with one foot.
This type of behaviour has been observed in other species and is thought to induce movement in worms and other prey, allowing the bird to detect them more easily.
Some ducks shake their heads rapidly when foraging in earth, perhaps achieving the same end.
Simmons, K.E.L. (1961) Foot movements in plovers and other birds. Brit Birds, 54(1), 34-39