Scientists find building blocks of birdsong's 'spectacular diversity'

Scientists in France say they have discovered the building blocks of the incredible diversity of birdsong.

A team analysed the songs of more than 100,000 songbirds and revealed that the world's birdsongs are composed of eight fundamental types of sound that the researchers call "motifs".

Birdsong all around the world, they say, is made up of combinations of these motifs - three types of trill, three types of whistle, chaotic notes and harmonies.

Birdsong is one of the natural world's most sophisticated forms of sound-based communication.

Its variety and complexity has fascinated biologists, but with so many different songs, it has been difficult to study on a global scale.

Lead researcher and University of Saint-Etienne PhD student Quentin Bacquelé explained: "The diversity is huge. And if you go to Asia, Africa, Amazonia, you will hear totally different songs."

In their new study, he and his colleagues used a global database of birdsong - recordings uploaded by thousands of volunteers. This meant they could analyse about 116,000 songs from more than 3,000 birdsong species.

They studied patterns in the songs - how each song shifted and changed through time. And with the help of AI, they could then compare the thousands of songs to each other - to find what connected them.

The scientists said this unveiled "a simplicity underlying the spectacular diversity of birdsongs".

A key finding was that the environment the birds evolved in - from tropical forest to temperate landscape - shaped how they "composed" their songs.

So birds adapted for tropical forests use different acoustic building blocks, or motifs, to those from temperate regions.

Simpler motifs, like flat whistles, Bacquelé explained, are often found in tropical environments, apparently because they help the birds make themselves heard through the busy, biodiverse soundscape and dense vegetation.

More complex compositions - with ultrafast trills and combinations that contain lots of information - are more common in temperate forests, where birds tend to communicate at closer range.

It's a kind of evolutionary trade-off: A very complex song provides a lot of information, but it is difficult to transmit that information over long distances in complex environments.

This link between the environment and its natural soundscape, Bacquelé explained, is being transformed by human activity.

"I think this research has opened up a new way to see songs as something [intrinsically] linked with the environment," he told BBC News.

"So, we could try to use these motifs to help us understand how birds could adapt to the new background noise [that we produce]."

Natural sound, Bacquelé added, is an an important part of our own connection to nature and is worth conserving.

"If you think of a forest, near your town or near your house, you think about the songs of the birds in the morning when you go outside.

"And if a bird in a forest has a specific song, if you destroy the forest, then that song may not be adapted any more to the new environment."

The study is published in the journal Science.