Rooks (Corvus frugilegus) can show spontaneous vocal flexibility when exposed to dynamically changing rhythmic sounds.

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 auditory rhythms. Most non-human primates have limited entrainment skills; its search in other taxa has shown cases of entrainment much more advanced than any non-human primate in a few taxa, among which birds. Finding convergently-evolved entrainment abilities in several species may highlight shared evolutionary origins. Here, we investigate spontaneous vocal entrainment in rooks, a social corvid, using non-biologically relevant stimuli. We exposed individual rooks to sound sequences varying in tempo and metrical structure, and tested the effect of these two manipulations on temporal adjustments in their song. Of the 11 birds tested, eight sang while listening to the stimuli. Three of them sang often enough for us to analyse their responses to most tempos and meters. We found that two of these 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 provides additional data on vocal flexibility in this vocal learning species. We cannot exclude that rooks may have attempted to vocally entrain, but the possibility will require further investigations. 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 convergently evolved building blocks of human musicality.