Acta Zoologica Sinica © 2006 Acta Zoologica Sinica

Abstract The production of complex bird song is commonly achieved through neuromuscular activity of respiratory, syringeal and craniomandibular systems. According to nonlinear dynamics theory, however, complexity can also emerge spontaneously from very simple and deterministic systems, without any external control. Thus far, studies linking bird song complexity with nonlinear dynamics are very rare. Here we explore the possibility that a number of complex acoustic phenomena in vocalizations of Streptopelia doves are caused by nonlinear dynamics intrinsic to their vocal organ. We show that the complex acoustic phenomena in species-specific coos resemble the nonlinear phenomena described earlier for mamma-lian vocalizations. These phenomena include the different attractor states that have been found in mammalian phonation (limit cycle, folded limit cycle, torus, and chaos), and sudden transitions within and between those states (bifurcations). We argue that large, qualitative differences between species-specific song in Streptopelia doves may correspond to different attractor states of the same type of dynamic system. If so, dramatic acoustic differences between species sounds do not necessarily reflect large differences in sound production mechanisms or evolutionary differentiation, but may be due instead to relatively small differences in syringeal structure and control mechanisms