Allometric trends reveal distinct evolutionary trajectories for avian communication

Acoustic signal production is affected by allometric relationships, by which the larger the animal, the lower its call frequency. In this paper, three evolutionary acoustic hypotheses were tested: the Signal-to- Noise RatioHypothesis (SNRH), in which evolution maximizes call ranges by increasing the signal-to- noise ratio; the Stimulus Threshold Hypothesis (STH), in which evolution maximizes the range of a specific signal threshold; and the Body Size Hypothesis (BSH), in which the emission of long wavelengths is enabled by body size. Three spectral metrics were measured, Dominant Frequency (FDOM), Minimum Fundamental Frequencies(FFMIN), and Maximum Fundamental Frequencies(FFMAX) of Neotropical Parrots, New World Doves, Woodcreepers, Tinamous, and Thrushes. A Ranged Major Axis (RMA) regression showed that body mass is significantly correlated with all of the spectral parameters in Parrots, Doves, and Woodcreepers, but only with the fundamental frequenciesof Tinamous. The FDOM of Parrots corroborated the ...