Say “Brrrr” but roll all the r’s. Now quickly add “Hm” with a sharp rising inflection, as if you’re indignantly questioning someone.

Congratulations: if you ever find yourself in northern Mozambique, you can now summon the greater honeyguide.

The honeyguide is a small African bird, whose scientific name—Indicator indicator—hints at its extraordinary behavior. It eats beeswax, and although it excels at finding bees’ nests, it can’t sneak past the stinging insects alone. Instead, it recruits humans. It approaches them, makes a loud “tirr-tirr-tirr-tirr” call, and flies in the direction of a nest. Throughout Africa, people have learned to follow it. They subdue the bees with fire and tools, and steal the delicious honey. To pay their avian guide, many of them leave pieces of wax behind.  This is arguably the greatest partnership between humans and any wild animal.

The first Western account of the honeyguide’s behavior dates back to 1588, when a Portuguese missionary based in Mozambique noticed a small bird pecking at the candlesticks in his church. It would also, he wrote, guide people to bees’ nests. Many people dismissed this account, and other anecdotes like it, as myths. That changed in the 1980s, thanks to Kenyan birder Hussein Isack and German zoologist Heinz Ulrich Reyer. Over three years, they followed the Boran people of northern Kenya as they, in turn, followed honeyguides.

Isack and Reyer showed that the Boran are experts at interpreting the honeyguide’s flight. Its direction tells the honey hunters where to head. If it makes itself more visible, flying off to nearer trees and perching on lower branches, the hunters know they’re getting warm. If the bird makes a unique indication call and then falls silent, the hunters know they’re pretty much next to a nest. Whether the bird signals distance deliberately or inadvertently, Isack and Reyer couldn’t say. But it almost doesn’t matter. By reading the birds’ behavior, the Boran can slash the average time it takes to find a bees’ nest from nine hours to just three.

They’re not the only people who benefit. Over the last decade, anthropologist Brian Wood from Yale University has shown that the Hadza of Tanzania also benefit from the honeyguide. The bird triples their odds of spotting a hidden nest, increases their honey-finding rate by more than six times, and leads them to richer nests that yield more than five times as much honey. Astonishingly, Wood calculated that the Hadza get up to 10 percent of their annual calories with the help of honeyguides.

Claire Spottiswoode

These studies clearly showed that the honeyguides provide useful signals to people. But what about the other way round? The Boran summon honeyguides by blowing into fists, snail shells, or palm nuts, creating a “penetrating whistle” that can be heard from over a kilometer away. But they use the same whistle to communicate with each other. As they walk through the bush, they talk and whistle to keep the bird’s attention—but again, those noises are part of their usual repertoire.

Not so in Mozambique. There, ornithologist Claire Spottiswoode from the University of Cambridge has learned that the Yao people use a distinctive “brrrr-hm” call for beckoning honeyguides—and nothing else. It’s a specific honey-hunting tradition, passed down from father to son. And the birds recognize the call. By playing various sounds through speakers, Spottiswoode showed that honeyguides are twice as likely to start guiding when they hear the brrr-hm call, compared to the more general sound of Yao speech. “They seem to understand what they’re being told,” says Spottiswoode.

“The call is used not just for attracting honeyguides,” she adds, “but for keeping the bird’s attention, for reassuring it that you’re still interested in keeping up the conversation.” If the honey hunters stopped brrr-hming, the bird often gave up. If they continued, they tripled their odds of finding a bees’ nest.

This is one of the few examples of a wild untrained animal attaching a meaning to a human signal, and responding appropriately.  In Brazil, fishermen catch mullet with the help of dolphins, which they signal by slapping the water. Hunters in the Canadian Arctic may once have cooperated with ravens in a similar way. But such instances are rare, and none have been studied as thoroughly as the alliance between honeyguides and honey hunters. Spottiswoode’s data “clearly provide solid validation for what were so far only assumptions,” says Edmond Dounias, who has watched the Baka pygmies of Cameroon interacting with the honeyguides.

It’s not clear how honeyguides learn to interpret the Yao signals, especially since they’re cuckoo-esque parasites. The females lay their eggs in the underground nests of bee-eaters, and their chicks always hatch first. When the young bee-eaters emerge, the honeyguide chick stabs them to death with a wicked spike on its bill. It can then monopolize the attentions of its foster parents.

This grisly habit, which Spottiswoode filmed in 2011, means that honeyguides have no opportunity for learning from their parents. She suspects that they’re born with the basics of guiding behavior, and then refine their technique by watching other adults in the vicinity of bees’ nests. They certainly seem to get better as they get older. The Yao say that the youngsters (which they treat as a different species thanks to their yellow feathers) are rubbish guides, and don’t respond to the Brrrr-hm. Only the adults are worth their time.

The Yao, like many other honey-hunting societies, make sure to reward their partners. “They make quite a song and dance about it,” says Spottiswoode. “They gather up bits of wax and present it on fresh, green leaves—a little honeyguide salad.”

The Hadza are an exception. In his work, Brian Wood never saw them paying their guides. Quite the opposite: they would often hide, bury, or burn any honeycombs they didn’t collect. This, they said, keeps the birds hungry and makes them more motivated guides.

Wood and Spottiswoode are now teaming up to study how human-honeyguide communications vary from place to place. “In some areas, birds are actively repaid by honey hunters and in other places and times, humans actively reduce the bird's payoff,” says Wood.

He thinks these partnerships are ancient ones, too. It’s hard to pin a date on them, but anthropologist Richard Wrangham thinks that they may pre-date our own species. A couple of million years ago, when early hominids mastered fire, they also gained a way of subduing bees by smoking them out. That could have set the foundations for our symbiosis with honeyguides. “There are a number of reports of honeyguides being stung to death by bees, so in the absence of fire, eating wax is a risky business,” says Spottiswoode.

But if that’s the case, what was the greater honeyguide doing before we came along? Genetic studies suggest that the it evolved three million years ago, well before any hominid started harnessing flames. It’s often said that honeyguides cooperate with other species like honey badgers but that’s a myth. It became popular knowledge after unscrupulous documentary-makers who filmed a tame honey badger interacting with a stuffed honeyguide. But in reality, there’s no evidence for such a partnership. You wouldn’t expect to find any either, since honey badgers have poor eyesight and hearing, and are largely nocturnal.

It should soon be possible to work out what honeyguides did before they guided. In many parts of Africa, people just get their honey from beekeepers. In others, they replace the stuff with sugar and other sweet food. “If you can do that, why bother finding wild bees’ nests and risk getting stung?” says Spottiswoode. “I’ve worked in Zambia, where the honeyguides are common, but there’s not a lot of guiding. It seems to be dying out, bit by bit.”