All birds in the world build their songs from the same eight sounds

Birds around the world use the same set of eight basic sound types for their songs. This is the conclusion reached by French and American scientists after analyzing nearly 117,000 recordings of songs from 3,160 species of passerine birds. The study was published in the journal Science.

Despite the enormous diversity of bird songs, researchers discovered recurring elements within them. They can be roughly compared to syllables in human speech. Three types are related to trills — slow, fast, and ultra-fast. Another three are related to whistles: steady, slowly pitch-changing, and rapidly modulated. The two remaining types were termed by the scientists as chaotic sounds and harmonic combinations of several notes.

"Most birds combine several such elements at once. On average, a single species uses 4.6 sound types, and about 65% of songs consist of at least two. At the same time, many birds have a favorite 'syllable': one sound type may appear in more than 80% of their songs," the scientists explained.

The researchers also found that the choice of sounds depends on the habitat. In dense tropical forests, simple whistles and slow trills are more common — they are better preserved over distance when sound passes through trees and humid air. In Europe and other temperate climate regions, by contrast, faster and more complex sounds are prevalent.

Bird songs are influenced not only by environmental conditions but also by lifestyle. Larger birds more often use simple sounds, while smaller ones are capable of producing fast and complex whistles. Social behavior also turned out to be an important factor: birds living in groups more frequently use similar sound elements.

In total, the scientists analyzed recordings of 3,160 species, covering more than half of all known passerine species. At the same time, the researchers emphasize that it is not yet known whether the birds themselves perceive these eight sound types in the same way the computer classifies them. Testing this will require experiments involving playback of recordings in the wild.