Madison Reporter

Researchers at the University of Wisconsin–Madison have conducted a comprehensive study to explore the diversity in bird vocalizations globally. The study, published in the journal Proceedings of the Royal Society B, utilized over 100,000 audio recordings from around the world to understand the factors influencing bird sounds.

The research focused on ecological and evolutionary traits such as body mass and beak size that affect how often bird species make certain sounds. H.S. Sathya Chandra Sagar, a doctoral student at UW–Madison working with Professor Zuzana Buřivalová, led this global analysis by examining recordings submitted to xeno-canto, a bird-watching repository. These recordings covered 77% of known bird species.

The study highlighted several key findings:

- Bird habitats impact sound frequency in unexpected ways. For instance, birds in areas with rushing water produce higher frequency sounds to avoid being masked by lower-frequency white noise.

- Birds living at similar latitudes tend to produce similar sounds. This pattern is significant for understanding the evolutionary development of bird vocalizations.

- Beak shape and body mass are crucial determinants of sound frequency. Smaller birds generally produce higher frequency sounds compared to larger birds, confirming existing hypotheses and providing new insights into these relationships.

Additionally, smaller bird species can produce a wider range of frequencies as a protective mechanism against predators. Higher frequencies aid communication within their species while lower frequencies may deceive potential threats about their size.

This research contributes to a broader understanding of soundscapes—comprehensive collections of sounds in an environment—which are important for conservation studies. Sagar emphasized that "there’s very little that we know about the forces that govern soundscapes." He hopes this work will pave the way for future studies aimed at improving ecosystem health monitoring through soundscapes.

Sagar also noted that larger birds hunted for meat typically call at low frequencies. A lack of low-frequency calls might indicate increased hunting activity in an area.

Future research plans include using 24-hour soundscape recordings to investigate if birds adjust their song timing amidst environmental noise. Sagar acknowledged the valuable contributions from birdwatchers and citizen scientists in enhancing our understanding of natural ecosystems.