The Physics of Birdsong

GABRIEL B. MINDLIN; RODRIGO LAJE

Springer

Año: 2005 p. 157

3540253998

Few sounds in nature show the beauty, diversity and structure that we find in birdsong. The song produced by a bird that is frequently found in the place where we grew up has an immense evocative power, hardly comparable with any other natural phenomenon. These reasons would have been more than enough to attract our interest to the point of working on an aspect of this phenomenon. However, in recent years birdsong has also turned into an extremely interesting problem for the scientific community. The reason is that, out of the approximately 10 000 species of birds known to exist, some 4000 share with humans (and just a few other examples in the animal kingdom) a remarkable feature: the acquisition of vocalization requires a certain degree of exposure to a tutor. These vocal learners are the oscine songbirds, together with the parrots and hummingbirds. For this reason, hundreds of studies have focused on localizing, within the birds’ brains, the regions involved in the learning and production of the song. The hope is to understand through this example the mechanisms involved in the acquisition of a general complex behavior through learning. The shared, unspoken dream is to learn something about the way in which we humans learn speech. Studies of the roles of hormones, genetics and experience in the configuration of the neural architecture needed to execute the complex task of singing have kept hundreds of scientists busy in recent years. Between the complex neural architecture generating the basic instructions and the beautiful phenomenon that we enjoy frequently at dawn stands a delicate apparatus that the bird must control with incredible precision. This book deals with the physical mechanisms at play in the production of birdsong. It is organized around an analysis of the song “up” toward the brain. We begin with a brief introduction to the physics of sound, discussing how to describe it and how to generate it. With these elements, we discuss the avian vocal organ of birds, and how to control it in order to produce different sounds. Different species have anatomically different vocal organs; we concentrate on the case of the songbirds for the reason mentioned above. We briefly discuss some aspects of the neural architecture needed to control the vocal organ, but our focus is on the physics involved in the generation of the song. We discuss some complex acoustic features present in the song that are generated when simple neural instructions drive the highly complex vocal organ. This is a beautiful example of how the study of the brain and physics complement each other: the study of neural instructions alone does not prepare us for the complexity that arises when these instructions interact with the avian vocal organ. This book summarizes part of our work in this field. At various points, we have interacted with colleagues and friends whom we would like to thank. In the first place, Tim J. Gardner, who has shared with us the first, exciting steps of this research. At various stages of our work in the field, we had the privilege of working with Guillermo Cecchi, Marcelo Magnasco, Marcos Trevisan, Manuel Eguia and Franz Goller, who are colleagues and friends. The influence of several discussions with other colleagues has not been minor: Silvina Ponce Dawson, Pablo Tubaro, Juan Pablo Paz, Ale Yacomotti, Ramon Huerta, Oscar Martinez, Guillermo Dussel, Lidia Szczupak, Henry Abarbanel, Jorge Tredicce, Pablo Jercog and Hector Mancini. The support of Fundacion Antorchas, Universidad de Buenos Aires, CONICET and ANPCyT has been continuous. Several recordings were performed in the E.C.A.S. Villa Elisa nature reserve in Argentina, with the continuous support of its staff. Part of this book was written during a period in which Gabriel Mindlin enjoyed the hospitality of the Institute for Nonlinear Science, University of California at San Diego. Heide Doss-Hammel patiently edited the first version of this manuscript, and enriched it with her comments. One of us (R. L.) thanks Laura Estrada, and Jimena, Santiago, Pablo and Kanky, for their continuous support and love. Finally, it was the support of Silvia Loza Montana, Julia and Ivan that kept this pro ject alive through the difficult moments in which it was conceived. Buenos Aires, April 2005.Gabriel B. Mindlin and Rodrigo Laje