Birdsong shares surprising similarities with human speech, music

Scientists have long recognised that some songbirds produce sounds with patterns resembling human speech and music. However, the reasons behind these similarities have remained unclear. A study published in Science on 29 October has now found that speech-like and musical patterns are widespread among birds, including species that do not learn their vocalisations from others.

Logan James, a postdoctoral researcher in the Department of Biology at McGill University in Canada and a co-author of the study, said birdsong has frequently been compared with human speech and music because all three involve sequences of sounds that require precise coordination, vary according to context and influence listeners.

However, most previous comparisons focused on a limited number of species, particularly birds capable of vocal learning. Consequently, scientists had been unable to determine whether these shared characteristics stemmed from vocal learning itself or from the physical and neurological processes involved in producing sound, James explained.

Thousands of recordings across hundreds of species

The researchers assembled one of the largest datasets used for this type of comparison, comprising more than 74,500 sound units from approximately 5,900 songs produced by 367 bird species across 52 families.

The sample included two groups capable of vocal learning — songbirds and hummingbirds — alongside two groups whose vocalisations do not depend on learning in the same way.

The team then compared these recordings with a global dataset of human speech and singing, containing more than 15,000 sound units from over 800 phrases across 52 languages.

According to James, the researchers examined four main characteristics: the size of pitch changes between consecutive sounds; rhythmic regularity; how sound duration, pitch and loudness change from the beginning to the end of a phrase; and whether these properties alternate between higher and lower values or remain relatively stable.

In human speech and music, people generally move between nearby pitches rather than making large jumps. Rhythmic patterns also tend to exhibit regularity, while sounds are sometimes prolonged towards the ends of phrases.

The researchers found that birds frequently exhibit similar patterns.

Changes in pitch between consecutive bird sounds were generally smaller than would be expected if the sounds were arranged randomly. Relatively regular rhythms also occurred more frequently than chance alone would predict.

Additionally, sounds towards the ends of bird songs tended to last longer, resembling the lengthening of final sounds in human speech and musical phrases.

These patterns appeared across different groups of birds, regardless of whether they learned their vocalisations.

This finding was particularly surprising because it challenges the assumption that vocal learning alone explains the similarities between birdsong and human communication.

Do birds communicate like humans?

The researchers emphasise that their findings do not mean birds speak or sing in the same way humans do. Rather, the study examined how sounds are organised through time, pitch and rhythm.

Direct comparisons revealed clear similarities between birds and humans, alongside important differences.

For example, pitch intervals were generally smaller in human singing, while the lengthening of sounds at the ends of phrases was typically more pronounced in human speech and singing than in most bird species.

Another unexpected finding emerged when the researchers examined the overall structure of vocal patterns rather than individual characteristics.

Across the characteristics studied, birdsong was generally more similar to human speech than to human singing in the way pitch and other sound properties changed over time.

Hummingbird vocalisations were also more similar to human speech and singing than those of some songbirds, which have traditionally been considered among the most useful animal models for studying human vocal communication.

James suggested that the widespread occurrence of these patterns, even among birds that do not learn their songs, may reflect shared physical constraints involved in producing complex sequences of sounds.

Both humans and birds must coordinate breathing, muscle movements and their vocal organs efficiently. These demands may encourage very different species to develop similar ways of organising sounds, even without inheriting those patterns from a recent common ancestor.

However, the study does not establish precisely which biological mechanisms account for these similarities.

The researchers examined a specific set of acoustic characteristics rather than more complex features, such as the hierarchical organisation of songs, the use of discrete musical pitches or musical scales.

They also identified substantial differences among bird species, which may be associated with body size, breathing mechanisms and the structure of their vocal organs.

Furthermore, the human comparison covered 52 languages and therefore did not encompass the full diversity of languages and musical traditions worldwide.

The findings suggest that some patterns shared by human speech, music and birdsong may arise from general constraints on sound production rather than vocal learning alone.

They also broaden the range of bird species that could help scientists investigate how complex vocal communication develops and why similar sound patterns emerge in animals separated by millions of years of evolution.