Why do some birdsongs sound beautiful while others do not? A new study suggests that the answer may lie in the sounds themselves.
Researchers in Germany asked 84 people to rate calls from 123 European bird species. They then compared the scores with four features of each call: loudness, pitch, complexity and bandwidth, meaning the range between low and high notes.
The results showed a clear pattern. Quieter calls with a higher pitch and a narrower range usually sounded more pleasant. More complex calls also received better scores. This was unexpected, because simple and repeated sounds might seem easier for the brain to enjoy.
The Eurasian blackbird ranked first, while the western barn owl came last. Other popular singers included the willow warbler, blackcap and mistle thrush. The participants did not need to know which bird they were hearing. Their knowledge of birds had little effect on their ratings.
Why might these sounds appeal to us? One idea is that varied but gentle birdsong signals a safe and healthy place where people can relax. Earlier research has also found that bird sounds can improve wellbeing and help people recover from stress.
The findings may have practical value. Designers of parks and other public spaces could think more carefully about their soundscapes. Conservation groups might also use well-liked birds as ambassadors for protecting wider habitats.
The study does not explain every personal preference. Still, it suggests that beauty in birdsong is shaped partly by measurable features, not only by memory or bird knowledge.