Japanese tits combine their calls using specific rules to communicate important compound messages, says an international group of ornithologists led by Rikkyo University scientist Toshitaka Suzuki.

“Language is one of humans’ most important defining characteristics,” said Dr. Suzuki and his colleagues from Sweden and Switzerland.

“It allows us to generate innumerable expressions from a finite number of vocal elements and meanings, and underlies the evolution of other characteristic human behaviours, such as art and technology. The power of language lies in combining meaningless sounds into words that in turn are combined into phrases.”

Research on the communication systems of non-human primates and birds suggests that the ability to combine meaningless vocal elements has evolved repeatedly, but the evolution of syntax was so far considered to be unique to human language.

A new study in Japanese tits (Parus minor) challenges this view.

“This study demonstrates that syntax is not unique to human language, but also evolved independently in birds,” said team member Dr. David Wheatcroft, a researcher at Uppsala University.

According to the scientists, Japanese tits have over ten different notes in their vocal repertoire and use them either solely or in combination with other notes.

“Our experiments reveal that receivers extract different meanings from ‘ABC’ (scan for danger) and ‘D’ notes (approach the caller), and a compound meaning from ‘ABC-D’ combinations,” they said.

“However, receivers rarely scan and approach when note ordering is artificially reversed (‘D-ABC’).”

The findings were published today in the journal Nature Communications.

“Understanding why syntax has evolved in tits can give insights into its evolution in humans,” Dr. Wheatcroft said.

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Toshitaka N. Suzuki et al. 2016. Experimental evidence for compositional syntax in bird calls. Nature Communications 7, article number: 10986; doi: 10.1038/ncomms10986