Meeting Abstract

P1.165  Monday, Jan. 4  Head-bobbing and terrestrial locomotion in charadriiform birds HANCOCK, Jennifer A.*; BIKNEVICIUS, Audrone R.; Marietta College, Marietta, OH; Ohio University, Athens, OH jah006@marietta.edu

Head-bobbing is the fore-aft movement of the head relative to the body during terrestrial locomotion in birds. It is predominately considered to be an optomotor response, in which the hold phase functions to stabilize an image on the retina and thrust phase is thought to use motion parallax to generate depth perception. However, previous studies have suggested that head-bobbing may be linked mechanically to aspects of locomotor biodynamics: (1) head movements are synchronized with limb movements in some species of birds and (2) locomotor mechanics differ in gulls walking with and without head-bobbing. The first goal of this study was to assess whether head-bobbing was synchronized with limb movements in free-ranging charadriiform birds while foraging. The second goal was to compare the kinematics of locomotion in head-bobbing and non-head-bobbing charadriiforms. Sixteen species (10 head-bobbers; 6 non-head-bobbers) were filmed in lateral view at 60 Hz, and the resulting videos were assessed for the timing of head and limb movements. The results found an imperfect synchronization of head and limb movements among head-bobbing charadriiforms; whereas the hold phase was predictably initiated near the onset of single limb support, the initiation of thrust phase was more variable. Furthermore, few significant differences were found between head-bobbing and non-head-bobbing species: stride duration and stance duration are similar although a speed-dependent difference in stride frequency is suggested.