Deceptive bird “lies” to steal food!
How can you spot a perfect con job? When the target (“mark”) is blissfully unaware, and doesn’t even recognize the deception, even after the fact.
“Conning and getting away with it” could be the mission statement for the fork-tailed drongo, a desert bird from Southern Africa. The drongo gets about one-quarter of its food from other birds — and a desert mammal called the meerkat. It does this by scaring the “rightful owners” away from their meals with an alarm call that would normally warn about a nearby bird or mammal predator.
And when the target flees, or even just scans the sky for the predator, the drongo swoops in and flies off with dinner. You might think the targets would figure this ruse out. You might be right, except the drongo is one step ahead: If the first alarm fails, it shifts to a different alarm call.
The drongo study, reported this week in Science, is the work of Tom Flower at the University of Cape Town. Since 2008, Flower has spent six months a year in the Kalahari desert (where he happens to be as we write), climbing sand dunes and enduring temperatures ranging from -11°C to 42°C.
As thick as thieves
The study site, dubbed Meerkat Manor, also hosts a long-term study of meerkats, a social mammal that eats insects and occasionally larger animals. At the Manor, meerkats, along with drongos and a bird with the oddball name pied babbler, have grown used to people gawking from close distances. “That means that I and other researchers can get right into the thick of the action,” Flower said in a press release. “We can unravel the interactions between all these animals because different individuals are identifiable by colored leg bands (in the case of the birds), or L’Oreal hair dye marks on the fur of the meerkats (don’t worry, it’s been tested on humans).”
The meerkat and pied babbler are both key targets for food theft by the drongos.
Drongos are no dummies, says Flower, who, with his co-author Amanda Ridley, has banded about 200 drongos living in 40 territories that overlap with meerkat and babbler turf. “I’ve trained the drongos to come to a call,” says Flower. “So if I want to find drongo ‘Dave,’ for example, I can walk into his territory, give a call and he’ll come flying over to me in return for a mealworm reward. He’ll rapidly get back to his natural behavior, hawking flies or following meerkats and babblers to steal their food, allowing me to tag along and watch what happens.”
Animals often respond to alarms from other species, and for good reason. News of a nearby predator concerns the entire suite of potential prey, and eavesdropping on alarms enables animals to spend more time feeding, and less time watching the trees and the sky.
Drongos are flexible: they emit six different alarm calls of their own, and can mimic up to 45 versions of alarm calls from other species.
When the researchers compared the effect of different alarm calls, they found that the babblers diverted their attention from their food for a longer when the drongo imitated the babbler’s alarm than when the drongo gave its own alarm.
To test the “crying wolf” effect, the researchers repeated an identical false alarm three times. The babblers seemed to recognize the deception, returning to their food more quickly. But that did not occur if the third alarm was different from the first two.
The con worked, Flower found. In 151 cases, the drongos repeated an attempted theft on the same target, and in 74 percent of those cases, the drongo chose another alarm, and changing the alarm raised the odds of future success. It’s a con that needs no polishing, and here’s the proof: The marks were fooled the next time around. Fool me once, shame on you. Fool me twice, shame on me!
– David J. Tenenbaum