Analysis of more than 116,000 bird songs has revealed that the astonishing variety of passerine birdsong is built from just eight basic acoustic motifs, like trills, whistles, and harmonic notes,. The findings also reveal that local environments greatly shape how birds communicate around the world. Birdsong is among nature’s most sophisticated and diverse forms of acoustic communication. Although bird songs have long served as a classic model for understanding the evolution of vocal communication, their immerse diversity has made it difficult to develop a unifying framework that helps to explain its complexity and why different acoustic patterns emerge in different environments. To address this question, Quentin Bacquelé and colleagues leveraged large-scale citizen science data and analyzed more than 116,000 songs from 3160 passerine species – the group that includes more than 60% of all bird species. They used a new approach that captures the full acoustic complexity of bird vocalizations. Rather than measuring only simple features such as pitch or frequency, Bacquelé et al. examined the detailed patterns of sound across time and frequency, allowing them to compare songs at an unprecedented scale.
The authors identified that most songs are built from just eight fundamental acoustic motifs, including different types of trills, whistles, harmonic notes, and more chaotic patterns. On average, each passerine species uses about five of the eight identified acoustic motifs in its song repertoire, and nearly two-thirds of all songs combine multiple motifs into more complex vocalizations. While most species rely heavily on one dominant motif across the majority of their songs, others use a more balanced mix of motifs, producing greater vocal diversity. What’s more, Bacquelé et al. found that the geographic distribution of these motifs reflects a balance between environmental constraints on sound transmission and biological pressures for effective communication. Structurally simple motifs, such as flat whistles, are favored in tropical rainforests where dense vegetation limits sound transmission. Complex motifs, including ultrafast trills, are more common in temperate regions where close-range communication and intense seasonal sexual selection favor more information-rich songs. The findings suggest that these basic vocal building blocks evolved early in passerine history and have since been repeatedly adapted to local ecological conditions. “Through combining large-scale citizen science data with a motif-based framework, Bacquelé et al . provide one of the most comprehensive analyses of passerine song evolution to date,” writes Elodie Briefer in a related Perspective. “In addition to advancing our understanding of avian communication, their approach could be used to study the evolution of complex acoustic systems across other biological groups.”
Science
The global biogeography of passerine songs
23-Jul-2026