Musical behavior consists of certain core phenomena, including the human tendency to entrain movement to an external auditory pulse. This ability is fundamental both for music production and for coordinated dance. The current literature claims that entrainment is a uniquely human capacity; here we correct this misconception, and report spontaneous motor entrainment to complex auditory stimuli in multiple avian species. In response to novel, natural human music, and in the absence of human movement, multiple avian subjects display significant rhythmic movement at the period and phase of the music across a range of different tempos. Since these animals entrain to music but do not do so in their natural behavioral repertoire, entrainment must have evolved as a byproduct of other cognitive mechanisms. All of our experimental subjects are proficient vocal learners, and thus these data support the idea that vocal learning mechanisms provide the necessary substrate for the entrainment capacity to emerge (Patel, 2006). To further investigate this hypothesis, we examined a corpus of videos on a large video database, and found numerous videos of birds moving at the period and phase of the music across numerous tempos and species. Critically, 100% of these videos involved vocal-learning birds; we found none such videos for vocal non-learning species. We also tested 16 cotton-top tamarin monkeys for spontaneous entrainment using the same stimuli that induced entrainment in avian subjects, as well as simple click-tracks, and found no evidence of entrainment. Together, these data strongly support the idea that entrainment is not unique to humans, and can emerge as a byproduct of other mechanisms, particularly the mechanism for vocal learning.