The changing chorus: How movements and memories influence birdsong evolution

(Press-News.org) New research from the University of Oxford has provided fresh insights into how bird songs evolve over time, revealing a significant role for population dynamics in shaping song diversity and change. The findings – based on an analysis of over 100,000 bird songs – have been published today (7 March) in the journal Current Biology. 

The researchers spent three years collecting over twenty thousand hours of sound recordings from a wild population of great tits (Parus major) in Oxfordshire, which has been studied for the past 77 years as part of the Wytham Great Tit study. Their aim was 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. 

To achieve this, 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. This 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 and the young birds that replace them can speed up the adoption of new song types. 

At the same time age serves as a brake on change, as older birds continue to sing song types that are becoming less frequent in the population. In this way, 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. 

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

Lead researcher Dr Nilo Merino Recalde (Department of Biology, University of Oxford) said: “Just as human communities develop distinct dialects and musical traditions, some birds also have local song cultures that evolve over time. Our study shows exactly how population dynamics - the comings and goings of individual birds - affect this cultural learning process, influencing both song diversity and the pace of change." 

The study is the first extensive test of the role of demography in driving cultural diversity and evolution at small scales in a wild animal population, using individual-level data and a very large dataset on song variation. This research not only provides insights into bird behaviour but also offers valuable perspectives on how demographic changes might affect cultural evolution across animal species - with potential implications for conservation efforts. The complete dataset has been made publicly available for other researchers to explore.   

Professor Ben Sheldon (Department of Biology, University of Oxford), who leads the long-term bird study in Wytham Woods, commented: “Our work here shows, once again, that tracking individuals over their lives allows us to understand so much of the way that different processes interact in natural populations. It’s thrilling to think that we can explain the acoustic landscape we hear in the woods each spring in terms of the result of the cumulative combination of individual movements and survival over many years.” 

Notes to editors  Interviews with Dr Nilo Merino Recalde are available on request: nilo.recalde@biology.ox.ac.uk 

The paper ‘The demographic drivers of cultural evolution in bird song’ will be published in Current Biology at 16:00 GMT / 11:00 ET Friday 7 March 2025. It will be available online when the embargo lifts at DOI 10.1016/j.cub.2025.02.016

To view a copy of the paper before this under embargo, contact nilo.recalde@biology.ox.ac.uk 

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