Difference between the vocalizations of two sister species of pigeons explained in dynamical terms
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Vocal communication is an unique example, where the nonlinear nature of the periphery can give rise to complex sounds even when driven by simple neural instructions. In this work we studied the case of two close-related bird species, Patagioenas maculosa and Patagioenas picazuro, whose vocalizations differ only in the timbre. The temporal modulation of the fundamental frequency is similar in both cases, differing only in the existence of sidebands around the fundamental frequency in the P. maculosa. We tested the hypothesis that the qualitative difference between these vocalizations lies in the nonlinear nature of the syrinx. In particular, we propose that the roughness of maculosa’s vocalizations is due to an asymmetry between the right and left vibratory membranes, whose nonlinear dynamics generate the sound. To test the hypothesis, we generated a biomechanical model for vocal production with an asymmetric parameter Q with which we can control the level of asymmetry between these membranes. Using this model we generated synthetic vocalizations with the principal acoustic features of both species. In addition, we confirmed the anatomical predictions by making post mortem inspection of the syrinxes, showing that the species with tonal song (picazuro) has a more symmetrical pair of membranes compared to maculosa.
KeywordsBiomechanics Birdsong Asymmetry Vocal control Nonlinear dynamics
We thank the Administración de Parques Nacionales and Fauna Authorities from Entre Ríos Province (Argentina), for authorizing permits for this study; the staff and rangers from Quebrada del Condorito National Park (Argentina), Darío Lijtmaer, Natalia Trujillo Arias, Diego Masson and Luciano Calderón for assistance in field work; and Adrián Di Giacomo, Natalia García, Priscila Hanisch and Belén Bukowski for help in taking care of the animals in captivity. We also thank Mr. Ramón Moller Jensen and El Potrero SA (Argentina) for allowing the fieldwork with pigeon specimens in the Natural Reserve. We are especially thankful with Fabián Gabelli for his advice and assistance with fieldwork and animal management. Yolanda Davies helped with captures, animal care, preparation and conservation of the specimens in the Ornithology Collection of the National Museum of Natural Science.
Compliance with ethical standards
Conflict of interest
The authors declare no competing or financial interests.
This work describes research partially funded by National Council of Scientific and Technical Research (CONICET), National Agency of Science and Technology (ANPCyT), University of Buenos Aires (UBA) and National Institute of Health through R01-DC-012859 and R01-DC-006876.
All experiments on animals described above were performed in accordance with applicable national legislation and institutional guidelines for the care and use of animals.
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