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Did complex song and dance co-evolve with brain size in the Birds of Paradise (Aves: Paradisaeidae)?

MacGillavry, Thomas1; Pelliconi, Federico2; Jønsson, Knud Andreas34; Nagombi, Elizah5; Field, Daniel J.6; Fusani, Leonida21

Published May 06, 2025 on Dryad. https://doi.org/10.5061/dryad.qz612jmsr

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Abstract

Complex signalling behaviors, such as avian song and courtship displays, have been associated with increases in both absolute and relative brain size, presumably mediated by relationships between brain size and motor coordination and learning abilities. Nonetheless, reliably establishing these relationships is challenging due to the difficulty of quantifying behavioral complexity. Birds of paradise perform some of the most elaborate avian courtship displays, involving a striking degree of complexity and motor coordination, which makes them interesting models for investigating the evolution of complex motor learning abilities in birds. Here, we compiled a μCT-based brain size dataset of more than half of the known species of birds of paradise and used multiple metrics of display complexity to test the hypothesis that larger brains are associated with more elaborate repertoires of motor and vocal displays. We found no clear evidence that the complexity of courtship display behaviors co-evolved with brain size among the birds of paradise: this conclusion held across three kinds of behavioral and two kinds of vocal complexity scores.