emu bob

Etymology
The motion of the people repeatedly bending down and standing up is likened to emus bobbing their head as they forage on the ground.

Noun

 * 1)  A task assigned to a group of people, especially schoolchildren or army recruits, where they move around an area and pick up rubbish from the ground.

Usage notes
Occasionally the term and its synonyms are applied to another activity which involves repetitive bending down over a wide area, such as searching for clues relating to somebody's disappearance.