Liar, liar, wings on fire: this intelligent desert bird survives on cunning
Once in Botswana, a southern African nation, I saw a troop of baboons making their way blindly through an overgrown field. The tops of their heads were barely above the tall grass, like the helmets of a military patrol ambushing. They were unaware of the presence of a cheetah cutting at an angle to cross them. I held my breath in anticipation. Then, all of a sudden, a bird – a small spoiler hornbill – gave a cry of alarm. Heads sprang up and the parties veered in opposite directions.
The idea that animals listen to alarm calls from other species is not new. Birds, mammals, and lizards do, and some species may even respond appropriately, depending on whether another species warns of an eagle or a snake. But a study published today in the journal Science shows a big step forward in this remarkable behavior with an account of the surprisingly complex “tactical deception” practiced by the fork-tailed drongo.
Drongos are a common bird species across sub-Saharan Africa. They are shiny black and the size of an American robin. They have a reputation for being fearless and will easily flee from raptors many times their size. “If they see an eagle, they shoot straight up into the air like a surface-to-air missile and cling to the tail,” says Tom P. Flower, behavioral ecologist at the University of Cape Town and lead author. of the new study.
Drongos feed mainly on insects, often hawking them in the air, for example around outdoor electric lights. But they are also kleptoparasites: that is, they steal food that other species have located or captured. It’s a common way of living in the natural world, and lions, hyenas, jackals, and of course vultures do it too, but none with the art and daring of the fork-tailed drongo.
In the Kalahari Desert, a drongo will frequently travel in mixed packs with southern magpie chatterers. They also associate with meerkats. These other species benefit, according to the study by Flower and her co-authors, because drongos produce honest warning signals at any sign of a predator approaching. So having a drongo perched high on a nearby bush means chatterers and ground meerkats can spend less time being vigilant and more time foraging.
But their drongo watchdog is also lying. Because he has a habit of saving lives with his honest warnings, his false alarms also cause chatterers and meerkats to scatter, just long enough for the drongo to scurry around and steal their food.
You might think it would only work for a little while. We all know from the legend of the boy who cried wolf, that repeating the same lie over and over again causes everyone to ignore you, even if you mistake it for the occasional truth. So, in addition to their own alarm calls, drongos have learned to mimic the alarm calls of no less than 45 other species. They collect this spectacular repertoire mainly from other local birds and, of course, from chatterers and meerkats.
Drongos are by no means the only successful vocal imitators in the animal world, nor even the only ones to use mimicry as a means of deception. Burrowing owls in the American West, for example, mimic rattlesnakes to deter potential predators from entering their nests. But the drongos deploy their mimicry with an unprecedented degree of tactical variation. For example, chatterboxes predictably become just a little skeptical of drongo alarm calls, and they will start foraging again faster than they do after the alarm call of a different species. . Drongos produce impersonated calls 42% of the time, according to Flower. Talkers also become skeptical when they hear the same type of alarm three times in a row. So when a drongo makes repeated attempts to steal food from the same target, it uses a different alarm call three out of four times.
What’s remarkable is that drongos go to great lengths to get just 23% of their daily diet. But Flower stresses that this is no small advantage in such a harsh and resource-poor environment as the Kalahari, especially in winter. It may seem like the drongos took this game to such an inventive degree, at least in part for their own amusement. But the most likely reality is that becoming a smart thief is all about survival.