Be it an arched eyebrow, a shaken head or a raised finger, humans wordlessly communicate complex ideas through gestures every day. This ability is rare in the animal kingdom, having been observed only in primates (SN: 8/10/10). Scientists now might be able to add a feathered friend to the club.
Researchers have observed Japanese tits making what they call an “after you” gesture: A bird flutters its wings, cuing its mate to enter the nest first. The finding, reported in the March 25 Current Biology, “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,” says biologist Toshitaka Suzuki of the University of Tokyo.
Suzuki has been listening in on the calls of Japanese tits (Parus minor) for more than 17 years. During his extensive time in the field, he noticed that Japanese tits bringing food to the nest would sometimes perch on a branch and flutter their wings. At that point, their partners would enter the nest with the flutterer close behind. “This led me to investigate whether this behavior fulfills the criteria of gestures,” Suzuki says.
Suzuki and Norimasa Sugita, a researcher at Tokyo’s National Museum of Nature and Science, observed eight mated pairs make 321 trips to their nests. A pattern quickly emerged: Females fluttered their wings far more often than males, with six females shaking it up while only one male did. Females almost always entered the nest first — unless they fluttered their wings. Then the males went first.
The birds also “never flutter their wings when they visit the nest alone,” Suzuki says. Fluttering happens only when birds are in the company of their mates, and they seem to direct their fluttering at their mate rather than at the nest entrance. This observation suggests that the Japanese tits aren’t pointing — a simple gesture that’s been seen in birds, like magpies and ravens, before, and is meant only to direct attention — but rather are communicating a complex message.
“I might think of this as an imperative gesture – a movement that communicates to another individual that they need to do something,” says primatologist Kirsty Graham of the University of St. Andrews in Scotland.
“It’s really exciting to uncover meaningful gestures in another species,” she adds. “I expect that we’ll probably find gesturing to be more widespread than previously thought.”
Gesturing by the nest instead of calling may help the birds avoid attracting predators, Suzuki says. He next wants to find out how wing fluttering fits into the tits’ larger communication repertoire. “In humans, gestures are used in combination with spoken language,” he says. “We are interested in understanding messages created by the combination of gestural and vocal communication in animals.”
