Here’s what you’ll learn when you read this story:
Birdsong is incredibly important for nearly every bird species on Earth, as it plays a role in mating and communication.
Now, scientists have discovered that birdsong actually follows a human linguistic trait known as Zipf’s law of abbreviation (ZLA), which explains the negative correlation between word length and usage.
The study analyzed 600 birdsongs across 11 populations—including seven different species—and found stronger patterns of ZLA across populations than in a single population.
Birdsong is an indelible instrument in the orchestra of nature, alongside rustling leaves, roiling waves, and the gentle hum of myriad invertebrates. And birds will use those songs for a variety of reasons—a lilting chirp attracts a mate, while a brassy screech warns of nearby predators. Similar to humans, language is central to all bird species, and even though we’re separated from these feathered friends by some 320 million years of evolution, birds have apparently picked up some linguistic tricks similar to our own.
A new study led by scientists at the University of Manchester shows that much like humans, birds follow a linguistic law known as Zipf’s law of abbreviation (ZLA), or the brevity law. Discovered by American linguist George Kingsley Zipf in 1945, the law describes the negative correlation between word length and usage frequency. For example, the most commonly spoken words in English (the, of, and, a, to, etc…) are generally shorter than less common words, such as antidisestablismentarianism. This is broadly true across all human languages, and University of Manchester’s Tucker Gilman—lead author of the new paper in the journal PLOS Computational Biology—believes the same can be said for birds.
“We know that birds and humans share similarities in the genes and brain structures involved in learning to communicate but this is the first time we’ve been able to detect a consistent pattern of ZLA across multiple bird species,” Gilman said in a press statement. “There’s still a lot more work to be done but this is an exciting development.”
One major difficulty in establishing ZLA in bird species is that birds have a much smaller vocabularies than humans, and types of vocal expressions can vary wildly among species.
So, to help make the analysis easier, the team relied on a new open-source computational tool called ZLAvian. But first, the team developed a new method for analyzing birdsong on the individual level rather than the population level. Then, Gilman and his team analyzed 600 birdsongs across 11 populations that included seven different species, including the California thrasher, redthroat, black-headed grosbeak, sage thrasher, Cassin’s vireo, western tanager, and gray strikethrush.
They found that when comparing vocalizations across populations, a stronger ZLA pattern emerged than the one that popped up when analyzing songs within a single population.
“Studying ZLA in birdsong is far more complex than in human language,” study co-author Rebecca Lewis, a conservation scientist at Chester Zoo in the U.K., said in a press statement. “Our research has taught that it’s important to look across a wide range of species when looking for language patterns and we hope ZLAvian will make it easier for other researchers to explore these patterns in more birds but also other animals in the future.”
This isn’t the first study to apply the brevity law to birds. In February of 2020, researchers led by the Equipe de Neuro-Ethologie Sensorielle of the University of Lyon/Saint-Etienne found that southern African Jackass penguins (named for their braying, donkey-like calls and not their personalities) also followed Zipf’s law as well as another linguistic rule known as Menzerath-Altmann Law, which states that intricate vocalizations are more likely composed of brief sounds than words with less vowels (i.e. “complimentary” vs “scrounged”).
“The laws seem to reflect something deeper and more general about communication and information,” Chris Kello, a linguist expert from UC Davis, told The Guardian at the time.
It appears that the exploration of that deeper connection is just getting started.
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