Studying macroevolutionary patterns of phenotypic variation and their driving forces in large radiations can shed light on how biodiversity is generated across broad spatiotemporal scales. In this study, we integrated song and morphological variation across more than 300 species representing the largest family of songbirds, the tanagers (Thraupidae), to uncover how morphological variables of the vocal tract combine to shape vocal evolution on a macroevolutionary scale. We found that body size correlated with multiple frequency parameters, concurring with past studies that show how body size constrains vocal evolution. Furthermore, bill size predicted multiple frequency and temporal song characters while bill shape was strongly associated with trill rates, suggesting that bill size and shape both constrain distinct elements of avian song independently of body size covariation. Our results demonstrate that the relationship between morphology and song exhibits modular variation when expanded to a macroevolutionary scale. Furthermore, our study emphasizes the need to consider multiple components of the avian vocal tract when exploring the macroevolutionary interplay of morphological traits and acoustic signals.

The dataset is a comma-separated file. Each species name follows the Clements 2016 checklist. "n.song" and "n.morph" show the sample sizes used for each species average. Each column, excluding "n.song" and "n.morph", are averages of measurements taken from multiple individuals of that species; furthermore, these averages have not been transformed. Song data (columns C:M) from left to right: average note length, average pause length, low (i.e., minimum) frequency, high (i.e., maximum) frequency, peak frequency, average note bandwidth, song bandwidth, frequency shift rate, maximum frequency shift, note rate, and trill rate. Morphology data (columns O:Q) from left to right: length of the left tarsus, Bill PCA 1 (bill size), Bill PCA 2 (bill shape). Additional details regarding song measurements and descriptions of each parameter are available in Supplementary Material Table S1. Morphological measurements were taken following the measurement practices described in Baldwin et al. (1931). Song data was quantified from spectrograms taken from the Macauley Library and xeno-canto.  "tarsus" denotes tarsus length. "PC1" and "PC2" denote the bill morphology principal components.

Missing values are denoted with an NA.