Relying on the humans to subdue the insects with fire and smoke, chop open the trunk, get the honey and then leave behind some beeswax that is a delicacy for the birds.
A small African bird that guides people to bees' nests hoping to share honey and wax responds to hunters' special calls in a rare example of a partnership between wild animals and humans, scientists said on Thursday.
Cooperation between the greater honeyguide bird and hunters was first written about by a Portuguese missionary in 1588, but was widely dismissed as pure hearsay. In recent years, however, researchers have found ever more evidence of the bond.
In Mozambique, hunters are far more successful in finding honey when they use a traditional call - a trill followed by a grunt that sounds like "brr-hm" - to attract honeyguides, the experts wrote in the journal Science.
Once attracted, the birds lead hunters to trees with bees, relying on the humans to subdue the insects with fire and smoke, chop open the trunk, get the honey and then leave behind some beeswax that is a delicacy for the birds.
In the 1980s, scientists documented that honeyguides seek human help by making distinctive calls and flitting from tree to tree to attract attention.
"We've found it's a two-way communication," lead author Claire Spottiswoode, an evolutionary biologist who works at Cambridge University and the University of Cape Town, told Reuters. "Humans communicate back to honeyguides as well."
The 'brr-hm' call "signals to honeyguides that they (hunters) are eager to follow. Honeyguides use this information to choose partners," she said.
The call doubles the chances of getting led by a honeyguide to 66 percent from 33 and increased the probability of finding a bees' nest to 54 percent from 17, compared to the use of other human or animal sounds to lure birds.
Most human cooperation with animals is with domesticated or trained animals, such as dogs or falcons. The only other known partnership with wild creatures is when dolphins sometimes work with fishermen, according to the study.
Spottiswoode said 20 Yao hunters interviewed in the Niassa National Reserve in Mozambique did not know the origin of the traditional "brr-hm" call. By contrast in Kenya, hunters whistle to attract the birds.
Still, honeyguides are not entirely sweet.
Like cuckoos, they lay eggs in the nests of other birds and baby honeyguides kill their foster siblings by stabbing them with sharp hooks on their beaks. Spottiswoode called them "the Jekyll and Hyde of the bird world."