A superb fairy-wren (left) attempts to drive away a cuckoo
David Ongley
Across the globe, over 20 avian species utilize a similar “whining” alarm call to alert others to the presence of broods like cuckoos. This call appears to carry cross-species understanding, indicating potential insights into the origins of language.
Cuckoos belong to a broad group of around 100 species recognized as brood parasites, laying eggs in nests of other birds and tricking the host birds into nurturing their chicks as if they were their own.
Research led by Will Feeney at the Doñana Biological Station, Spain, has discovered that 21 bird species, all of which share a common ancestor from approximately 53 million years ago, employ similar “whining” vocalizations upon detecting a brood parasite.
These species include superb fairy-wrens (Malurus cyaneus) from Australasia, tawny-flanked prinia (Prinia subflava) from Africa, Hume’s leaf warblers (Phylloscopus humei) from Asia, and greenish warblers (Phylloscopus trochiloides) from Europe.
“It’s fascinating that such diverse birds from different corners of the world are converging on a similar vocalization to represent their respective brood parasites,” Feeney notes.
The study showed that species producing this alarm call often reside in regions with numerous brood parasites that target various host species. When potential hosts hear the whining call, they respond aggressively, attempting to drive away the intruder.
“Brood parasites pose a unique threat; they can greatly endanger your offspring without being a direct threat to you,” Feeney explains. “Our findings indicate that the call aims to rally other birds quickly, potentially for assistance.”
“For superb fairy-wrens, which are cooperative breeders, it’s likely that the mobbing call is designed to invite other individuals to join in the defense,” states Rose Thorogood from the University of Helsinki, Finland.
In further investigation, Feeney and his team played recordings of alarm calls from brood-parasite hosts from different continents to possible host birds in Australia and China. They found that hearing these foreign warning calls triggered just as swift a mobbing reaction as calls from their own species.
“This demonstrates that the function of this vocalization facilitates cross-species communication rather than being limited to within-species interactions,” Feeney observes.
Thorogood cautions, “It may not necessarily indicate an ancestral shared alarm for brood parasites, but rather that a specific acoustic trait is effective at driving them away.”
The team conducted a similar playback experiment with yellow warblers (Setophaga petechia) in North America, known to host brown-headed cowbirds (Molothrus ater), but which do not emit the characteristic whining alarm call. When exposed to the superb fairy-wrens’ alarm calls, the warblers returned to their nests swiftly, similar to their response to other distress calls, rather than mobbing.
Feeney suggests this implies an innate element within the alarm calls that many bird species respond to, but birds in areas where brood parasites are prevalent have adapted their calls and responses to convey local threats.
“They’ve adapted a distress call into a novel context of offspring threat,” he adds, “which might explain why birds globally use a similar sound.”
Charles Darwin theorized in his 1871 book The Descent of Man that spoken language origins could stem from the imitation and alteration of instinctive sounds animals make. For instance, a squeal due to fear or a scream in pain. “The adaptation of these innate calls for another purpose might represent a stepping stone towards language,” says Feeney.
Rob Magrath from the Australian National University comments, “Calls frequently hold particular meanings, sometimes referring to external objects or events instead of merely expressing internal emotions, like fear or identifying sex or species.”
“This referential quality makes these calls similar to human words, which typically denote external objects or events,” he adds. “Thus, animal communication and human language may exist on a continuum rather than language being exclusively a human trait.”
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