Nonlinear phenomena and song evolution in Streptopelia doves

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 emergespontaneously from very simple and deterministic systems, without any external control. Thus far, studies linking bird songcomplexity with nonlinear dynamics are very rare. Here we explore the possibility that a number of complex acousticphenomena in vocalizations of Streptopelia doves are caused by nonlinear dynamics intrinsic to their vocal organ. We showthat the complex acoustic phenomena in species-specific coos resemble the nonlinear phenomena described earlier for mammalianvocalizations. These phenomena include the different attractor states that have been found in mammalian phonation (limitcycle, folded limit cycle, torus, and chaos), and sudden transitions within and between those states (bifurcations). We arguethat large, qualitative differences between species-specific song in Streptopelia doves may correspond to different attractorstates of the same type of dynamic system. If so, dramatic acoustic differences between species sounds do not necessarilyreflect large differences in sound production mechanisms or evolutionary differentiation, but may be due instead to relativelysmall differences in syringeal structure and control mechanisms.

Gabriel J.L. Beckers, Carel ten Cate, Acta Zoologica Sinica 52(Supplement): 482-485, 2006