By Victoria Gill
Science and nature reporter, BBC News
Drongos often follow groups of meerkats as they forage
Drongos in the Kalahari mimic the alarm calls of other species in order to steal food, scientists have found.
The birds "play tricks" on meerkats in particular, following the little mammals around until they catch a meal.
The drongos then make fake alarm calls that mimic other species and cause the meerkats to run for cover, allowing the drongos to swoop in.
The findings are reported in the journal Proceedings of the Royal Society B.
The scientists suggest that by mimicking other species, drongos keeps their deception "believable".
"It's a nifty trick," said Tom Flower, the Cambridge University PhD student who carried out the research.
He began his work studying meerkats in the Kalahari Desert and quickly noticed their reaction to the drongos' alarm calls.
When a predator was in the area, the birds could make an alarm call and the meerkats would immediately dash for cover in boltholes.
"But when the drongos saw a meerkat with a large food item such as a gecko, larvae or even a scorpion, it would make a false alarm call that sounded the same as the calls they made at predators, even though there were no predators around," he told BBC News.
The researcher then turned his attention to the drongos. He followed and studied 100 birds, and discovered that they mimicked the alarm calls of several other species.
This appeared to persuade the meerkats that there was a dangerous predator in the area and they should abandon their food and hide.
Mr Flower likened the discovery to one of Aesop's fables. "Using your own alarm call won't get you too far - just like the boy who cried wolf - the responder will stop listening to you," he explained.
To avoid being ignored, the birds appear to deliberately change the type of call they make - to alter the species they mimic - when meerkats stop responding to their alarm calls.
"This might keep their deception racket going, increasing their food stealing profit," said Mr Flower.
"It would be like the boy in Aesop's fable mimicking the voice of another villager when he cried wolf in order to continue fooling the villagers."
Although most of the species they impersonated were other birds, drongos even managed a meerkat alarm call. Mr Flower thinks the birds may have learned by trial and error that meerkats are likely to find their own alarm call "particularly convincing".
This is one of the first studies to show a function for vocal mimickry.
"It's very common in birds, but [previously] we had no idea why they did it," said Mr Flower.
Dr Laura Kelley from Deakin University in Geelong, Australia, told BBC News that this was first study to demonstrate conclusively that false alarm calls could be used as a foraging strategy.
"About 20% of songbirds mimic and as yet we know little about how this mimicry functions in many species," she commented.