It happens in birds separated by great geographical distances and millions of years of evolution. They share a similar learned vocal signal to identify parasitic enemies near their nests. The secret vocalization of birds is the first known example of its kind. It is an animal vocalization learned from an innate response shared by multiple species.
The research is in Nature Ecology and Evolution. Describe how natural selection influences vocal communication systems. The study is from Cornell University and the Doñana Biological Station.
Brood parasitism occurs when birds, such as cuckoos, lay their eggs in the nests of other species. They force the host to raise their young. Often at the expense of their own young. Therefore, it is advantageous for the host species to identify and try to prevent nest parasites from laying eggs.
Secret bird vocalization was studied in more than 20 different species of birds on four continents. They produce almost identical "whining" vocalizations when detecting a parasitic bird in their territory.
When a bird hears the warning call, it instinctively goes out to investigate. Thus, birds begin to absorb the signals that surround them, which is called social transmission. "When birds absorb cues around them, they learn when to produce the sound in the future," they say.
«This call is an intermediate point. It is between the instinctive vocalizations of animals and fully learned vocal units. Like human words," they add.
Language of the world
These species live in areas with complex networks of interactions between brood parasites and their hosts. «The birds collaborate to scare away the parasites. So communicating how and when to cooperate is essential. This call is appearing in areas of the world where species are more affected by breeding parasitism," they explain. "The evolution of the whining call is affecting patterns of cooperative behavior among birds around the world."
"It's like seeing how evolution can allow species to give learned meanings to sounds." The findings challenge long-held assumptions about the clear divide between animal communication systems and human language. The authors suggest that learned communication systems, such as human language, could have evolved through the gradual integration of instinctive and learned elements.
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