The sound of birds singing can make people feel calmer and more comfortable. Yet certain bird calls appear to be especially enjoyable to human listeners, and scientists are starting to identify the reasons behind that response.

Throughout much of human evolution, the everyday sounds of birds may have served as a comforting sign that the area nearby was safe and relatively free from threats.

New research suggests that particular acoustic traits may explain why some bird songs appeal to people more than others. In a small study, researchers at the University of Tübingen in Germany found that participants generally favored quieter calls with a narrower range of frequencies. At the same time, more elaborate vocalizations were often judged to be more pleasant.

The researchers also found that listeners’ preferences did not seem to depend on how familiar they were with birds.

“This indicates that the pleasure we get from birdsong may be linked to something deeper than simply recognizing the species we are hearing,” said Dr. Nadine Kalb, the study’s lead author.

Kalb explained that no single sound quality determines whether a bird call is enjoyable. Instead, listeners appear to respond to different combinations of acoustic traits, which can together create sounds that humans find especially pleasing.

The findings may help scientists better understand the role birds play in human surroundings. Over time, they could also influence the design of parks, city green spaces and other environments intended to support relaxation.

“One of the key messages is that noticing birds can transform how we experience nature,” said senior author Dr. Christoph Randler. “Even if we do not know what a bird is signaling, its voice can capture our attention, create positive emotions and make us more aware of the life around us.”

Why the common blackbird ranked highest

For the study, researchers asked 84 participants to listen to recordings from 123 species of wild birds and evaluate how pleasant they found each vocalization.

The common blackbird, also called the Eurasian blackbird, received the highest average score: 4.52 out of 5. Often found in gardens, parks and wooded areas, Turdus merula is common across Europe and is known for its warm, smooth, flute-like song.

At the opposite end of the ratings was the barn owl, which earned an average score of 1.32. Its call is often described as a harsh, unsettling screech. Other highly rated birds included the European goldfinch, with a score of 4.26, the European robin at 4.04 and the blue tit at 3.92.

What causes one bird’s voice to sound beautiful while another seems less appealing? That was the main question Kalb and Randler, a biology professor at the University of Tübingen, set out to investigate.

“Our work grew from a broader interest in why interactions with birds can feel so positive for people,” Randler said. “Earlier studies had already suggested that birds and birdwatching may contribute to restoration and psychological well-being.”

In this study, the team focused more directly on the sounds themselves, combining the biology of bird vocalizations with the psychology of human hearing. After participants rated the recordings, researchers compared those scores with measurable sound features to identify the characteristics associated with more melodic or pleasant calls.

Randler said one of the most unexpected results involved complexity. People often rated more intricate songs as more pleasant. “It may seem logical that simple, repetitive sounds would be easier to process and therefore more enjoyable,” he said, “but the results pointed in the other direction: complex vocalizations often received higher scores.”

Listening more closely to birdsong

The research could eventually encourage planners and landscape designers to reconsider how sound is handled in busy urban areas. Rather than concentrating only on reducing unwanted noise, they may also need to consider the positive sounds people encounter, including naturally occurring bird calls.

Still, Randler emphasized that this area of research remains at an early stage. Simply broadcasting bird sounds in public areas may not create the same benefits as hearing birds naturally. Earlier work by his team found that added birdsong played through speakers did not improve well-being more than real birdsong already present in an environment.

“Bird voices matter in ways that go beyond communication among birds,” Randler said. “They are also an important part of the soundscape that humans experience every day.”

Dr. Olga Feher, an associate professor of psychology at the University of Warwick who studies birdsong, said the results indicate that human preferences may have at least some biological basis. Feher was not involved in the study.

She noted that other research has suggested that responses to sound can be shaped by deep evolutionary history. Studies have found that humans and other animals can share preferences for particular vocal qualities, while separate research has identified rhythmic similarities between human music and birdsong.

However, Feher said personal history can also influence what people enjoy. She studies zebra finches, whose quick, mechanical-sounding songs are often considered less attractive. “I personally enjoy them very much,” she said, adding that positive associations likely play a role.

She cautioned that using birdsong preferences to shape public environments should not lead people to value only species with conventionally beautiful calls. A strong focus on melodic or charismatic birds could unintentionally harm conservation attention for species whose voices are less appealing to human ears.

“What I find most compelling is that this research may reveal something about how our sense of beauty evolved,” Feher said. “It may also be something we share with songbirds, which sing to attract and impress members of their own species.”

Dr. Robert Lachlan, an animal communication researcher and associate professor of psychology at Royal Holloway, University of London, said the work opens an interesting new direction but requires further investigation before scientists can explain exactly why certain bird songs appeal to humans.

He questioned whether higher-pitched sounds are always more attractive, pointing out that birds famous for their singing, including blackbirds and nightingales, often produce lower, flute-like notes.

“There may be particular parts of the frequency range that people naturally find more appealing,” Lachlan said. Looking only at the upper and lower limits of a song’s frequencies may miss those more specific preferences, he added.

He also said that both biology and lived experience probably affect the way people respond to birdsong. Although birdwatching experience did not change preferences in this study, familiar sounds may still carry emotional meaning. Hearing recognizable neighborhood birds after returning home from a trip, for example, can feel distinctly different from hearing unfamiliar calls.

Kalb said the results show that there is no universal recipe for a beautiful bird sound. “The blackbird, willow warbler and blackcap all sound quite different, but each received very high pleasantness ratings,” she said. “What matters is not one feature on its own, but the way frequency, volume and bandwidth work together in a bird’s vocalization.”

Randler agreed that many questions remain. The study identifies sound traits linked with pleasantness, but it does not yet explain why the human brain responds favorably to those traits. Future research may explore whether the same preferences appear across cultures, landscapes and different listening contexts.