The vocal repertoire of the domesticated zebra finch: a data-driven approach to decipher the information-bearing acoustic features of communication signals
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Although a universal code for the acoustic features of animal vocal communication calls may not exist, the thorough analysis of the distinctive acoustical features of vocalization categories is important not only to decipher the acoustical code for a specific species but also to understand the evolution of communication signals and the mechanisms used to produce and understand them. Here, we recorded more than 8000 examples of almost all the vocalizations of the domesticated zebra finch, Taeniopygia guttata: vocalizations produced to establish contact, to form and maintain pair bonds, to sound an alarm, to communicate distress or to advertise hunger or aggressive intents. We characterized each vocalization type using complete representations that avoided any a priori assumptions on the acoustic code, as well as classical bioacoustics measures that could provide more intuitive interpretations. We then used these acoustical features to rigorously determine the potential information-bearing acoustical features for each vocalization type using both a novel regularized classifier and an unsupervised clustering algorithm. Vocalization categories are discriminated by the shape of their frequency spectrum and by their pitch saliency (noisy to tonal vocalizations) but not particularly by their fundamental frequency. Notably, the spectral shape of zebra finch vocalizations contains peaks or formants that vary systematically across categories and that would be generated by active control of both the vocal organ (source) and the upper vocal tract (filter).
KeywordsVocalization Songbird Acoustic signature Meaning Classification Regularization
We would like to dedicate this study to Peter Marler and Richard Zann and Allison Doupe. By his fundamental discoveries and his thoughtful contributions to the field of animal communication, Peter Marler has been a major source of guidance and inspiration for our own research efforts in the field of bird communication. In his seminal Science paper in 1967, Peter Marler said: “We are beginning to understand how the structure of animal signals relates to the function they serve.” We would hope that Peter would agree that we are humbly following his footsteps. Peter Marler is the scientific great-grandparent of FET and great–great-grandparent of JEE. Richard Zann dedicated his life to the study of wild zebra finches in his native Australia. Allison Doupe developed the zebra finch model in crucial seminal studies that examined the neural mechanism of vocal plasticity. She was the scientific parent of FET and grandparent of JEE. She was an outstanding mentor and a wonderful person. We would not be able to appreciate the complexity and the relevance of our studies without their respective contributions to the field. Richard Zann died in a bushfire inferno that occurred in outskirts of Melbourne in February 2009. Peter Marler died in July 2014 following a long illness. Allison Doupe died in September 2014 after a long battle with cancer. This work was supported by an NIH grant CD010132 to FET, a CRCNS NSF grant IIS1311446 to FET and JEE and a fellowship from the Fyssen Foundation to JEE.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national and/or institutional guidelines for the care and use of animals were followed. All animal procedures were approved by the Animal Care and Use Committee of the University of California Berkeley and were in accordance with the NIH guidelines regarding the care and use of animals for experimental procedures.
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