Birds worldwide share the same warning call against nest invaders

Birdsong may seem like simple music, but it serves a deeper purpose. Communication in the wild can mean survival, especially when predators or intruders threaten vulnerable nests.

A new study has revealed that some of these calls are not just instinctive outbursts but shared lessons learned across species and continents.

An international research team has discovered that birds separated by geography and millions of years of evolution produce the same vocal warning when confronted by parasitic enemies.

This finding is the first known example of an animal vocalization that combines both innate and learned elements across multiple species.

Warning signals evolved independently

Brood parasitism is a reproductive trick. Birds like cuckoos and cowbirds lay their eggs in the nests of other species. The unsuspecting host parents raise these intruders, often at great cost to their own young. For a host species, the ability to detect and prevent parasitism is vital.

The researchers found that more than 20 species across four continents use nearly identical whining calls to signal the presence of parasitic birds. From Australia to China to Zambia, this shared vocal alarm emerges despite the fact that these birds never meet.

The consistency raised a critical question: how did such similar signals evolve independently?

Learning from others

When one bird hears the whining alarm, it instinctively investigates. This reaction creates an opportunity for social learning. Damián Blasi, a language scientist at Pompeu Fabra University, calls this process social transmission.

“It’s then, when birds are absorbing the clues around them, that the bird learns when to produce the sound in the future,” said James Kennerley, co-lead author of the study and postdoctoral fellow at the Cornell Lab of Ornithology.

This discovery also hints at the value of community responses in evolution. By copying the alarm of others, younger or inexperienced birds quickly learn which sounds carry danger, and which situations demand immediate action.

Midpoint between instinct and language

William Feeney is an evolutionary ecologist at Donana Biological Station and co-lead author of the study. According to Feeney, what makes the whining call fascinating is its position between automatic cries and learned communication.

“The fascinating thing about this call is that it represents a midpoint between the instinctive vocalizations we often see in animals and fully learned vocal units like human words,” said Feeney.

This midpoint helps scientists better understand how communication evolves. For example, human infants cry instinctively, but words are learned. Birds producing a sound that is both innate and taught offers a rare glimpse into this evolutionary transition.

Birds share the warning call

The study also revealed that species using the whining call often live in regions with dense networks of brood parasite interactions.

“With birds working together to drive parasites away, communicating how and when to cooperate is really important, so this call is popping up in parts of the world where species are most affected by brood parasitism,” Kennerley explained.

Such cooperation is not limited to birds. In mammal societies, alarm calls often spread across herds or groups, but usually each species develops its own repertoire. What makes this bird study striking is the convergence of the same call across so many unrelated lineages.

The outcome, noted Kennerley, is that the evolution of the whining vocalization is affecting patterns of cooperative behaviors between birds around the world.

Rethinking animal communication

The discovery blurs long-held boundaries between animal communication and human language. By showing how learned responses can evolve from instinctive calls, the findings highlight a possible path toward complex communication systems.

“For the first time, we’ve documented a vocalization that has both learned and innate components, potentially showing how learned signals may have evolved from innate calls in a way first suggested by Charles Darwin,” said Feeney. “It’s like seeing how evolution can enable species to give learned meanings to sounds.”

The study challenges the view that human language is a sudden evolutionary leap. Instead, it suggests that language may have grown through gradual steps, with early signals carrying both instinctive urgency and learned meaning. Birds, in this sense, may represent a living example of what those early steps looked like.

Beyond bird warning calls

For birdwatchers and scientists alike, this discovery changes how we think about the soundscape of forests and fields.

A simple whining note may now be recognized as part of a global pattern, echoing across species that share no recent ancestry. It also raises new questions. Could other animal groups share similar hybrid signals, waiting to be identified?

The work from Cornell University and Donana Biological Station does not just describe a curious case of mimicry. It opens a window into the evolution of learning itself.

By tracing how birds combine instinct with social learning, scientists can better understand the origins of communication – and perhaps the early roots of our own language.

The study is published in the journal Nature Ecology & Evolution.

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