Newspaper article The Christian Science Monitor

Chirping with Syntax: Do Bird Calls Work like Human Language?

Newspaper article The Christian Science Monitor

Chirping with Syntax: Do Bird Calls Work like Human Language?

Article excerpt

Birds may communicate surprisingly like humans.

In human language, the combination and order of words helps shape the meaning of a sentence. And bird calls may use similar structure.

Compositional syntax, combining different words to communicate a compound meaning, was thought to be unique to human language. But Japanese great tits, particularly vocal songbirds, also use compositional syntax in their bird calls, according to a new study published Tuesday in the journal Nature Communications.

"Our study shows, for the first time, that birds, like humans, use the rules of syntax to chat with others. This finding reveals an unsuspected degree of semantic complexity in avian vocal communication," study lead author Toshitaka N. Suzuki, says in an email to The Christian Science Monitor.

Birds twitter, chirp, peep, warble, and sing to communicate the location of a food source, to warn that danger is near, or to woo mates. But how exactly do birds vocalize particular complex meanings?

Dr. Suzuki and his colleagues had noticed the Japanese great tit using different sounds and different combinations of sounds in a variety of contexts. "We wondered if these calls, like human language, are comprised of different elements with distinct meanings," he says.

Great tits are in the same family as chickadees and produce calls that are similarly structurally complex. So the researchers listened and broke down the great tits' calls into notes to better understand how they were used individually and together in a string.

Note types dubbed A, B, C, and D are used together to form calls. The team observed that A, B, C notes are usually used in combination with others, so a call would be AB, BC, or ABC. But D notes were often in a string of seven to 10 notes forming a call, DDDDDDD.

To understand the calls' meanings, the team observed how the birds responded to hearing certain recorded calls projected over a loudspeaker. Birds hearing an ABC call would scan the horizon looking for a predator or some other danger. And a D call triggers the bird to move toward the source of the call, perhaps having been told to come find a food source or join a mate in their nest.

The researchers hypothesized that combining the two calls into ABC-D would produce a compound meaning, and demonstrate compositional syntax. And they were right. When the birds heard an ABC-D call, they simultaneously scanned the horizon and moved toward the sound.

But the birds could have simply been responding to both calls separately rather than as a compound unit. So the researchers reversed the calls, forming a D-ABC unit, to see if the birds reacted in the same way.

They found that the order matters.

When the researchers played a D-ABC call, the great tits rarely scanned the horizon or approached the sound. …

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