Rapid adjustment of pecking trajectory to prism-induced visual shifts in crows

Summary statement The mechanisms underlying birds’ pecking skills are not known. We examined whether pigeons and crows adjust their pecking to the visual distortion caused by prisms. We found that vision plays a role only before movement begins in pigeons, whereas crows may have more flexible visuomotor skills. ABSTRACT Pecking in birds is analogous to reaching and grasping movements in primates. Although pecking in pigeons is highly stereotypic, crows show dexterous pecking skills. To unveil what sensorimotor mechanisms underlie the flexibility of pecking in crows, the current study examined whether pigeons and crows adjust their pecking to the visual distortion induced by prisms. Because prisms induce visual shifts of object positions, birds were required to adjust their movements. Pecking kinematics were examined before and after attaching prisms in front of the birds’ eyes. As a result, crows showed faster adjustment of pecking trajectories than pigeons. Correlational analysis showed that the initial deviation of trajectory strongly influenced the subsequent deviation in pigeons, but not in crows. These results suggest that pecking in pigeons is controlled in a feedforward manner, and vision plays a role before movement initiation, although pecking in crows is under the on-line motor control, serving a possible mechanism for flexible visuomotor skills.