According to research, the sound of birds is shaped by evolution and environment. (TTL nature)
Birds may sound different, but scientists have now found that many of their songs are built on the same basic set of sound patterns. A new global study has identified eight recurring motifs that appear in the songs of thousands of bird species.
This also explains why birds that live in forests sing differently from those that live in open landscapes.According to research, the sound of birds is shaped by evolution and environment. The bird inherits many of its song traits from its ancestors and where it lives also plays an important role. Dense forests, humidity and long communication distances can affect how sound travels, prompting birds to use songs that are easier to hear.
The findings, published in the journal Science, are based on one of the largest studies of bird sounds ever conducted. The researchers analyzed more than 116,000 song recordings from 3,160 species of passerine birds collected from around the world through citizen science projects.
A global framework for birdsong
Birdsong is more than just a nice background sound. Birds use songs to attract friends, defend their territories, and communicate with competitors or neighbors.
For these messages to be useful, the sounds must carry information and also travel well through the environment until they reach another bird.Scientists have studied bird song for many years, but most previous research has focused on simple measurements like pitch or frequency. According to the researchers, this approach missed many important details that make each song meaningful.In this study, bird sounds were treated as information rather than just sound.
Aside from looking at pitch, the scientists also analyzed how frequency and timing changed during each song. This allowed them to compare songs from thousands of genres using the same method.
Why were passerine birds chosen?
The researchers studied passerines, also known as passerines or songbirds. Passerine birds include more than 6,000 species and represent more than 60% of all bird species on Earth.They are also found in almost every terrestrial habitat, from tropical rainforests to open grasslands and mountains.
Because they live in different environments, they have helped understand how habitat affects bird sounds on a global scale.The recordings used in the research came from open source citizen science databases, allowing researchers to study bird communications across continents.
The study focused on passerines, also known as passerines or songbirds.
Eight building blocks of birdsong
To compare songs, scientists used an automated sound analysis method. They examined each recording using the modulation power spectrum, a technique for measuring how sound changes over time and across different frequencies.According to the analysis, most bird songs are made of combinations of only eight recurring phonetic forms. These ornaments are building blocks that birds assemble in different ways, just as musicians arrange notes into different melodies.The eight elements include three types of chants played at different speeds, three types of whistles with different pitch changes, and two more complex sounds described as chaotic out-of-tune chimes and harmonic stacks.Most genres use more than one idea in their songs. In fact, researchers found that individual songs typically contain between two and eight themes.However, one motif often dominates. The researchers found that 65.3% of the genres used their main theme in more than 80% of their songs. The remaining 34.7% of genres used a wider mix of motifs, resulting in greater diversity in their songs.
Location affects singing
After identifying the eight elements, the researchers looked at where different song styles were most popular.
They found that birds that communicate over long distances usually rely on simpler sounds. This included flat whistles and slow trills that traveled farther without losing clarity.On the other hand, birds that communicate over shorter distances often produce faster and more complex songs. These include ultrafast trills and harmonic stacks, which carry more information. However, they become deformed more easily as they travel.Researchers say this indicates a trade-off. Birds can either produce highly detailed songs that carry more information or simpler songs that are better transmitted over long distances.
Challenges of rainforests and open landscapes
The study also found differences between tropical and temperate regions. Birds that live in tropical rainforests generally use simpler songs. Dense vegetation and humid air make it difficult for complex sounds to be transmitted without distortion.
As a result, birds in these habitats choose sounds that remain clear even after passing through dense forests.In contrast, birds living in temperate regions used faster and more complex whistles and trills. Scientists say that these sounds break down more easily over distance, but birds use them because they may not need to communicate over such long distances.The researchers believe this difference may also be related to stronger competition for mates in temperate regions.
The role of evolution
Although habitat influenced bird sounds, the researchers found that evolution remained the strongest influence. By comparing bird songs with species’ family relationships, body characteristics and mating systems, the team found that lineage, or evolutionary history, explains 82% of the variation in song forms.The study also found smaller but consistent differences associated with mating systems. Species in which a single male mates with multiple females were more likely to use certain rapidly changing whistles and other complex song patterns.This suggests that birdsongs evolve through a combination of inherited traits, environmental conditions and behaviour.
