Anyone who’s taken a hike in the woods has likely heard bird alarm calls. When our little feathered friends notice us, or perhaps or canine companion, they make high-pitched sounds and dive into the bushes. Other eavesdropping avians take a hint from their vigilant winged neighbors and follow suit, even before they see us coming, a new study finds.
At least one species of bird—the superb fairy wren, a beautiful black and blue species found on Australia’s east coast—can learn new alarm calls without directly experiencing a threat, according to a study published this week in the journal Current Biology. In an example of "social learning" the birds learned the alarm by ear, without ever seeing a predator or the species putting out the alarm, reports Christina Larson at the AP.
In recent decades, researchers have learned that those alarm calls are more complex than we ever thought. Chickadees, for example, can indicate the size of an approaching predator through their calls and many species eavesdrop on other types of birds, or even chipmunks, to find out if there’s a fox or Cooper’s hawk in the neighborhood. And it’s not just an innate ability; some birds learn the alarm calls of their neighbors after associating the exclamations with the presence of a predator.
“We knew before that some animals can translate the meanings of other species’ ‘foreign languages,’ but we did not know how that ‘language learning’ came about,” co-author Andrew Radford at the University of Bristol tells Larson.
In the study, the researchers looked at the superb fairy wren, a beautiful black and blue species found on Australia’s east coast. According to a press release, previous studies had showed the bird was capable of learning new alarm calls if they were exposed to views of a predator when exposed to the alarm. For this experiment, the researchers made the threat more abstract. At first, they exposed 16 tagged birds in the Australian National Botanic Gardens in Canberra to novel alarm sounds, one computer generated buzz and a real alarm from the allopatric chestnut-rumped thornbill, a native bird that fairy wrens don’t normally respond to.
The fairy wrens did not react to either noise when first exposed. Then the thornbill alarm was broadcast alongside alarm calls familiar to the little birds over the course of three days, causing them to dive into the bushes. Later, when the thornbill alarm was sounded on its own, the birds looked for cover 81 percent of the time while only seeking shelter 38 percent of the time when they heard the computer-generated control buzz. Over the following week, the birds still responded strongly to the warning.
That indicates that the fairy wrens were indeed superb, at least in learning, and had figured out that the call was also an alarm using context clues from listening to other birds.
Larson at the AP explains the process well:
To put it in human terms, it’s as though a person who only speaks English had learned that “Achtung” means “attention” or “danger” in German simply by listening to people yell phrases with similar meanings in multiple languages at once.
“Alarm calls warn of predators, but here the birds learnt the meaning of the call from the alarm calls of others without needing to see the predator,” Robert Magrath of the Australian National University and co-author says in the release. “This means it is a type of ‘social learning,’ where individuals learn from others rather than through direct experience. In this case, it’s even more indirect, because they only need to hear and not see the birds giving the familiar alarm calls. So theoretically they could learn with their eyes closed!”
It’s likely that the fairy wren, superb or otherwise, isn’t the only bird that can engage in social learning. “Fairy-wrens are smart—but they definitely aren’t the most intelligent bird species,” Dominique Potvin, lead author of the study tells Ryan F. Mandelbaum at Gizmodo. “So, I think we could safely generalize these results to other birds, especially other songbirds.”
In fact, it’s not surprising that birds engage in social learning, and the result was expected. That’s because in wild situations predators are often only seen fleetingly, if at all. It would be strange if birds could only learn alarm calls while staring at a fox or cat that was stalking them. “If you can only learn in the presence of a predator, that’s quite dangerous," Radford tells Larson. “The capacity to learn by associating sounds with meaning makes sense, biologically.”
It could also have implications for conservation as well. According to the release, many endangered bird species reared in captivity and released into the wild become quick lunches for predators. That may be because they simply have not learned the alarm calls of other species in the neighborhood. Using “social learning,” those birds could be trained to recognize alarm calls before heading off into the big, scary world.