Bird Calls Syntax: Study Reveals Complex Communication

Birds can develop calls with syntax that allow them to communicate important compound messages to each other, researchers believe they have found after examining calls from the Japanese great tits for a study published in the science journal Nature Communications this week.

Researchers found that the Japanese great tit has a wide vocal repertoire and an evolved syntax, according to a statement from Sweden's Uppsala University. Researchers stated that the Nature Communication study was the first experimental evidence for compositional syntax in a non-human vocal system.

"This small bird species experiences a number of threats, and in response to predators, they give a variety of different calls," the Uppsala University statement said. "These calls can be used either alone or in combination with other calls."

Researchers found that "ABC calls" were made to signal a "scan for danger," according to Uppsala University, such as when spotting a perched predator. Researchers said the bird would give "D calls" as a "come here" signal when they discover a new food source or to woo a partner to their nest box, for example.

Tits often combine the two calls when approaching and deterring predators, whether in their natural order or even reversing the order to mean different things, researchers noted.

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

Great tits and chickadees are from the same family and produce calls that are similarly structurally complex, the researchers said. The researchers said they broke down the calls into notes in an effort to understand how they were used individually and together.

"These findings demonstrate that Japanese great tits have evolved compositional syntax by which different meanings are combined into a compound meaning through a note-ordering rule," Suzuki said.

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