What if your co-worker was a bird?

In many parts of Africa, humans and wild honeyguide birds have developed a symbiotic relationship. Human honey-hunters call for the birds, which guide them to honeycombs. The humans collect the honey, leaving the waxy combs for the birds to gobble up.

Now, researchers have found that the honeyguide birds are much more responsive to local human calls than outsiders, suggesting the birds recognize a local dialect. They outlined their findings on December 7 in the journal Nature. 

Co-lead author Claire Spottiswoode, an evolutionary biologist at the University of Cambridge’s Department of Zoology and the University of Cape Town, has been studying the honeyguide bird-human hunter relationship for years in Mozambique.

There, local Yao hunters call for the birds using a sort of trill whistle followed by a grunt.

Spottiswoode already knew that honeyguide calls vary in different locations throughout Africa. Different people across the continent use different calls to attract the birds to help gather honey. She set out to discover whether the birds are more likely to respond to calls from local people than outsiders.

She teamed up with Brian Wood, a honeyguide researcher from the University of California Los Angeles and the Max Planck Institute for Evolutionary Anthropology, to study this question in two specific areas: the Kidero Hills of Tanzania and the Niassa Special Reserve in Mozambique.

In their experiments, they played different honeyguide calls on a speaker while they walked along honey hunting routes in Mozambique and Tanzania. They found that honeyguide birds are very picky about local calls.

The researchers found that honeyguide birds in Mozambique were “almost twice as likely” to cooperate with hunters using the local Yao grunt and trill than the hunters who used the Hadza whistle from Tanzania. 

The same was true in Tanzania: There, the birds responded to the local Hadza whistle three times more often than the Yao grunt. 

"I was quite astonished when we saw together how discriminating the Tanzanian honey guides were," she said. "It was almost uncanny how strongly they preferred the beautiful whistle melodies of their local Hadza partners compared to either the foreign sounds used by (other) Hadza hunters or arbitrary human sounds."

Spottiswoode said this is like human language.

"Findings suggest that communication between humans and other species can assign meaning to arbitrary sounds in a similar manner to human language," said Spottiswoode.

"The key thing for both language and these interspecies signals is that everyone agrees what the sounds mean," she continued. "So it seems that such social conventions improve our ability not only to cooperate with other humans, but also with other species. And I think most honey hunters would be quite unsurprised by these findings."

Edited by: Fred Schwaller