THE BIRDSONG CONUNDRUM

Conservation Scholar, Becky Lewis (University of Manchester), published the first paper of her PhD, exploring the importance of avian vocalizations for conservation.

With 13% of global bird species classified as threatened by the International Union for the Conservation of Nature (IUCN), conservation NGO’s around the world, including Chester Zoo, seek to act to prevent bird extinction. Generating successful conservation outcomes requires a deep understanding of an animal species. As research continues, we begin to learn more about previously cryptic traits or variations that we must account for in actions. This is the beginning of one such story.

Much like how human language varies massively across the world, avian vocalizations not only vary between species, but also between populations of the same species. Slight differences in syllables, pitch or phrases can make all the difference to birdsong.

All birds that are vocal learners – those that learn songs from other individuals – are likely to show some level of vocal dialect over time. Consider how in a human game of ‘Chinese Whispers’, often messages are warped and shifted due to variation along the chain of communication. Birdsong is similar, with variations occurring naturally as songs are passed between generations or social groups. We call this ‘cultural drift’.

As vocalizations have impacts on survival, they are affected by natural selection and evolution. Thus variation between populations is expected to occur naturally when geographically separated over multiple generations due to both cultural drift and natural selection.

While fascinating to study, this variation brings challenges in the context of conservation.

Population-specific vocal dialects can impact on key behaviours for survival and breeding, including territory formation and mate choice. Research studies have shown that male birds defending a territory are far more likely to respond aggressively to dialects similar to their own than those they do not recognize, suggesting they would fail to adequately respond to invasion from an unrecognized foreign intruder. Similarly, females selectively choose mates that they perceive to have a similar dialect. In a small, threatened population, breeding may fail if dialects between the available males and females are too distinct.

The challenge lies in the nature of traditional conservation strategies that involve bringing animals from different locations to form breeding populations in either ex-situ collections, or in-situ as the result of translocations and reintroductions.

When populations of various geographic dialects are mixed, there is significant risk that if birds cannot effectively communicate due to differences in dialect, then these populations may not be successful. Birds of one dialect introduced to a geographic area where a population of a different dialect is already established may not integrate and breed with the existing inhabitants, and could even begin to directly compete – effectively hastening extinction rather than preventing it.

SO HOW DO WE SOLVE THESE CHALLENGES?

Becky’s research is now looking at Java sparrows in ex situ breeding programmes to understand the factors affecting bird accents and the steps we could take to reduce these challenges in conservation programmes. There are numerous approaches to take. Firstly, it is important to understand the range of dialects in this species, how vocalizations change during ex situ conservation and what factors contribute to any differences. Then, understanding how birds perceive dialect differences will help us to determine how differences in vocalizations could affect newly formed populations, and to devise strategies to mitigate any problems that could arise.

Stay tuned as we follow and support her research through the next two years.

Becky’s work is funded by NERC, Chester Zoo and the University of Manchester President’s Doctoral Scholarship with additional funding from the Daiwa Anglo-Japanese Foundation and the Japan Society for the Promotion of Science.

PUBLICATIONS

Lewis,R., Williams, L., Gilman,T., 2020 The uses and implications of avian vocalizations for conservation planning. Conservation Biology.