In the dense canopy of a Brazilian rainforest, a bird delivers a series of clear, flat whistles. Thousands of kilometres away, in the forests of equatorial Africa, another species produces almost the same simple sounds. This convergence is no coincidence. A study published in the journal Science on 23 July 2026 has shown that the extraordinary variety of passerine birdsong worldwide rests on just eight basic acoustic motifs.
These motifs function as a shared vocabulary. Slow trills, fast trills, ultrafast trills, flat whistles, slow-modulated whistles, fast-modulated whistles, harmonic stacks and chaotic notes combine in different proportions to create the songs familiar to birdwatchers on every continent. According to the analysis, songbirds use an average of five of these building blocks. Two thirds of species mix multiple types rather than relying on a single motif.
The patterns are not random. Birds in tropical forests tend toward simpler elements such as flat whistles, while those in temperate regions favour more complex structures including ultrafast trills. The same simple acoustic patterns appear in similar ecological conditions across continents, even when the locations lie thousands of kilometres apart. This consistency points to deep order within what at first appears to be boundless diversity.
Trade-offs shaped by environment and biology
The choice of motifs reflects a practical trade-off. Some sounds travel farther through dense vegetation but carry less information. Others convey greater complexity yet degrade more quickly over distance. Environmental factors, particularly vegetation density, interact with biological traits such as body size and mating systems to determine which combinations prevail.
The research examined more than 116,000 songs from over 3,000 passerine species. Machine learning techniques allowed the team to process a global database of recordings uploaded by volunteers. The scale of the dataset revealed patterns that smaller studies had missed.
A French-led team including Quentin Bacquelé of the University of Saint-Étienne analysed the global dataset and concluded that these eight motifs underpin the diversity of birdsong, with environmental adaptation shaping motif use.
Bacquelé, the lead researcher, captured the finding neatly.