Learning pathway determines motor organization and long-term retention of tool use in hornbills

Social learning is widely used to explain behavioral traditions, yet whether it determines their long-term stability remains unclear. This study tested this in hornbills learning a novel stone-dropping tool task by dissociating individual reinforcement from action-based demonstration by a human experimenter. Hornbills did not innovate after exposure to the solved outcome alone. Although both routes enabled acquisition, they generated different motor solutions and sharply different retention. Individually trained birds solved rapidly using push-based insertions, whereas socially trained birds learned more slowly and adopted grab-lift actions matching the demonstration. After 12 months, all socially trained birds retained the behavior, whereas none of the individually trained birds did. Observing organized action may therefore promote the consolidation of novel behavior into durable, tradition-like forms.