These Small Birds Flutter Their Wings to Say ‘After You’ to Their Partner

When a mated pair of small birds called Japanese tits arrives at the nest, one of them might flutter its wings at the other. The second bird then typically enters the nest first. This motion might be a signal, meant to convey the message “after you” to the other bird, scientists reported Monday in the journal Current Biology.

The research provides the first evidence of animals besides primates using gestures to communicate meaning. The result “shows that Japanese tits not only use wing fluttering as a symbolic gesture, but also in a complex social context involving a sender, receiver and a specific goal, much like how humans communicate,” Toshitaka Suzuki, a co-author of the new study and a biologist at the University of Tokyo, tells Science News’ Darren Incorvaia.

Humans use gestures for a variety of reasons. Some are meant to point out objects, known as deictic gestures, and others are for conveying messages, called symbolic gestures. Great apes use a range of gestures as well.

Scientists have also observed ravens and fish using deictic gesturing to point out something of interest, according to a statement from the University of Tokyo. But symbolic gestures, such as waving goodbye, are more cognitively demanding, and researchers were unsure whether non-primates could use them.

Suzuki has been studying Japanese tits for more than 17 years. He observed the birds using different calls to convey meaning and even combining the calls into phrases that follow rules of grammar, per the university’s statement. After that finding, he was compelled to study whether the creatures used physical gestures, too.

He noticed that sometimes a tit bringing food to the nest would sit on a branch and flutter its wings, after which its partner would enter the nest first, followed by the flutterer, per Science News. “This led me to investigate whether this behavior fulfills the criteria of gestures,” Suzuki tells the publication.

These birds gesture "after you" | Science News

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In a forest where the birds live, the researchers have installed hundreds of nest boxes that mimic the tree cavities the birds typically reside in, writes New Scientist’s Chen Ly. Only one bird at a time can fit through the entry hole.

For the new study, the researchers observed more than 320 nest visitations from eight mated pairs that were bringing food to the nests to feed their offspring. The researchers found that females more frequently performed the fluttering, after which the male would usually enter the box first—regardless of which bird was first to arrive at the site. If the female didn’t flutter her wings, she would typically enter the box first.

The motion also had certain traits of communication: Birds only fluttered when their mate was present, stopped fluttering once the mate entered the box, didn’t physically touch their mate and only gestured toward the other bird, not the box. Together, these observations suggested to the researchers that the fluttering qualifies as a symbolic gesture.

“They’ve done a really good job here of showing there is an association between this movement, this gesture, and then … the other bird doing something,” Mike Webster, an ornithologist at Cornell University who was not involved in the work, says to Scientific American’s Olivia Ferrari. “It’s a really strong support to the notion that it’s a symbolic gesture. The bird that’s the receiver knows what it means, and it does what it’s supposed to do.”

“I might think of this as an imperative gesture—a movement that communicates to another individual that they need to do something,” Kirsty Graham, a primatologist at the University of St. Andrews in Scotland who did not contribute to the findings, tells Science News. “It’s really exciting to uncover meaningful gestures in another species,” she adds to the publication. “I expect that we’ll probably find gesturing to be more widespread than previously thought.”

The findings suggest that further research should be done on animal gestures, which could provide insight into the origins of language.

“There is a hypothesis that language evolved from gestural communication,” Suzuki says to New Scientist. “So, these studies can help us understand the evolution of complex communication, including our own language.”

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.