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Remarkable adaptations in plants and animals
An adaptation is the answer a lineage has reached to a particular problem, and the same problem is often answered the same way. What stands here now is bird song: machine learning across more than 3,000 songbird species found that every song in the world is built from eight basic motifs, and that ancestry decides which of them a bird uses.
What shapes an adaptation
- A signal has to reach its receiver through whatever lies in between, so the habitat sets limits on what will carry.
- Sexual selection acts on traits that win mates rather than on traits that keep an animal alive, and it pushes those traits towards elaboration.
- Body size fixes the physical range of what an animal can produce, so size often predicts the form a signal takes.
- What a lineage has already inherited limits what it can evolve next, so close relatives often carry the same solution even where they live far apart.
What shapes a bird's song
Simple motifs
- Flat whistles and slow trills
- Larger birds
- Birds signalling over long distances
- Tropical rainforests, where song must carry through dense vegetation
Complex motifs
- Small birds
- Birds signalling at close range
- Groups under intense sexual selection
- Temperate Europe and North America, with small territories and short breeding seasons
What has happened
2 Sep 2026
Machine learning on recordings of more than 3,000 passerine species found that the world's bird songs are built from eight basic motifs.
- The recordings came from Xeno-canto, a citizen science audio library, and the eight motifs are three trills, three whistles, atonal chaotic notes and harmonic stacks.
- Which motifs a bird uses is decided mostly by its evolutionary history rather than by where it lives.
- Indian passerines such as the house crow (Corvus splendens) and the red-vented bulbul (Pycnonotus cafer) are Least Concern on the IUCN Red List.