Rooks (Corvus frugilegus) spontaneously attempt to vocally entrain to rhythmic stimuli

Musicality is the predisposition to process and produce music. In human beings, processing and producing music often involves entrainment, the ability to synchronise behaviour to external rhythms. Non-human primates generally exhibit poor entrainment skills, which may be due to their relative lack of vocal learning. Focusing on non-primate species like songbird species, is one way to investigate further the evolution of musicality. Here, we investigate spontaneous vocal entrainment in rooks, a social corvid, using non-biologically relevant stimuli. We exposed individual rooks to non natural sound stimuli and tested the effect of various tempos and metrical structures on their willingness to sing along, and on their capacity to entrain (singing along the tempo or the meter, or both). Several individuals sang while listening to the stimuli. Among them, two individuals were influenced by particular tempi and/or metrical structures: one bird produced shorter vocalisations at slower tempo and another reduced the intervals between its vocalisations upon hearing isochronous sequences with a unary metre and slow tempo. Still, the timing of the start of their vocalisations did not match accurately the timing of the beat of the stimuli. Our results suggest that rooks attempted to vocally entrain, an as-yet rare demonstration of vocal flexibility, even among open-ended vocal learners. Despite their evolutionary distance from humans, rooks, and possibly other corvids and songbirds, are interesting species for future studies on rhythmic perception, and could help shed light on the evolution of musical abilities.