Watching a hermit thrush forage for food on the floor of a forest, you might notice a strange behavior. The bird will stand still and rapidly shake on of its legs. The behavior is known as “foot-trembling” and it’s used to induce insects to move in order to reveal their location.
In celebration of #ThrushDay, please enjoy this short clip of a hermit thrush foraging for insects on an unseasonably warm December afternoon in #UpstateNY. This behavior, known as "foot trembling," wakes dormant insects, revealing their location to the hungry bird. pic.twitter.com/Vtmt9be0Jo
— Brandon Tate (@SilverWolf_47) December 27, 2018
Other birds like the Piping Plover and the Ringed Plover also use foot-trembling behavior to scare up prey out of the sand along beaches. Sometimes referred to as “foot-tapping” or “foot-pattering”, the movements help to bring worms and other prey closer to the surface of the sand. There is some debate among researchers as to whether this activity causes the worms to move closer to the surface or if it’s the vibrations from the foot-trembling that move the worms to the surface.
In this video below, you can see a Piping Plover demonstrate foot-trembling by rapidly tapping one leg over the surface of the sand. The Plover alternates tapping its legs as it hunts for worms. Periodically, the bird notices movement in the sand and dips its beak into the sand to retrieve the prey.
Osborne, B. C. (1982). Foot-trembling and feeding behaviour in the Ringed Plover Charadrius hiaticula. Bird Study, 29(3), 209-212. DOI: 10.1080/00063658209476759
Simmons, K. E. L. (1961). Foot-movements in plovers and other birds. Brit. Birds, 54(1), 34-39.