Tracing how bird songs evolved

How do bird songs evolve? New research from the University of Oxford has provided fresh insights, revealing a key role for population dynamics in shaping song diversity and change.

The researchers spent three years collecting over 20,000 hours of sound recordings from a wild population of great tits (Parus major) in Oxfordshire. They form a part of a collection of 100,000 such songs collected over the years.

The researchers wanted to investigate how the movement, age, and turnover of birds within a population influences the diversity and evolution of their songs —including which songs become locally popular, which fade away, and how varied their song repertoires become.

They used a new approach involving training an AI model to recognise individual birds based on their songs alone and measure song differences between individuals. The method allowed them to track variations in song repertoires across the population and uncover patterns in song evolution.

The results showed that birds of similar age tend to have more similar repertoires, with mixed-age neighbourhoods having higher cultural diversity. Furthermore, the pace of song turnover within neighbourhoods is driven by individuals coming and going. When birds leave or die, many song types disappear with them. The young birds that replace them can speed up the adoption of new song types.

Also, age serves as a brake on change, as older birds continue to sing song types that are becoming less frequent in the population. Thus, older birds can function as ‘cultural repositories’ of older song types that younger birds may not know, just as grandparents might remember songs that today’s teenagers have never heard.

However, age is not the sole factor influencing song change. The study also found that when birds mix more—through increased local dispersal and the arrival of immigrants—they tend to adopt more common songs, which also slows the pace of song evolution.

‘Homegrown’ songs tend to stay unique: Areas where birds stay close to their birthplace maintain more diverse and unique song cultures, similar to how isolated human communities often develop distinct dialects or musical styles.

The results indicated that newcomers tend to adapt but also enrich song diversity. Immigrant birds typically adopt local songs rather than introducing entirely new tunes. However, they tend to learn more songs overall, enriching the local ‘musical scene.’

“Just as human communities develop distinct dialects and musical traditions, some birds also have evolving local song cultures. Our study shows how population dynamics—the comings and goings of individual birds—affect this cultural learning process, influencing song diversity and the pace of change,” said lead researcher Nilo Merino Recalde from the Department of Biology, University of Oxford. The findings have been published in Current Biology.