How Birds Sing — and Why

Among the study’s major takeaways is that bird species’ habitat influences the frequency of the sound they may make. Madhu Venkatesh, Wildlife Conservation Action Team

Birds make sounds to communicate — whether to find a potential mate, ward off predators, or just sing for pleasure. But the conditions that contribute to the immense diversity of the sounds they make are not well understood.

Researchers at UW–Madison have conducted the first-ever global study of the factors that influence bird sounds, using more than 100,000 audio recordings from around the world. The new study revealed insightful patterns for why birds make certain noises and at what frequency.

Hypotheses about the role of habitat, geography, body size, and beak shape in forming bird sounds have been tested on a small scale. But H. S. Sathya Chandra Sagar PhDx’24, who works with Assistant Professor Zuzana Buřivalová in the Department of Forest and Wildlife Ecology and the Nelson Institute for Environmental Studies, wanted to see if they held up on a global scale.

Sagar analyzed audio recordings of bird sounds taken by people around the world and submitted to a bird-watching repository called xeno-canto. The recordings represented 77 percent of known bird species.

Among the study’s major takeaways was that bird species’ habitat influences the frequency of the sound they may make. For example, in ecosystems with a lot of rushing water there is a constant level of white noise occurring at a lower frequency. In such cases, researchers found that birds tend to make sounds of higher frequency, likely so they won’t be drowned out by the water.

Another finding is that bird species living at the same latitudes make similar sounds. Observing this pattern at a global scale is an important piece of the puzzle in the evolutionary story of bird sounds. It could inspire further research into the aspects of geographic location that influence sound.

The research also contributed to the broader understanding of soundscapes — all the sounds heard in any particular landscape. Sagar hopes this foundational work will provide a platform for future studies to improve conservation efforts by developing ways to monitor the health of an ecosystem through soundscapes.

Published in the Summer 2025 issue