This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Vultures were long thought to make few and fairly simple sounds. Yet no one had investigated in detail how the birds use sound to communicate.
For his master's thesis in Jorg Massen's Vulture Cognition Lab, Connor Proudfoot studied the critically endangered Rüppell's vulture. He and his colleagues found that the birds produce a wide range of complex sounds, which they use in a range of social situations. The findings, published today in PLOS One, could help improve the success of captive breeding programs and shed light on the evolution of communication.
When you think of a vulture, you might picture a solitary bird perched silently on a branch or soaring through the sky. But some vultures are highly sociable. For example, Rüppell's vultures, found in the Sahel and East Africa, live in flexible social groups and breed in colonies of up to 1,000 birds.
"Within the groups, there's a hierarchy: some birds rank higher than others," says Proudfoot. "In such a large colony, the animals also sometimes form smaller groups to forage together. And when they find a carcass, they often encounter dozens of other vultures and have to compete for a place.
You would expect a species living in such a complex social environment to have sophisticated ways of communicating, so we decided to look into that." Proudfoot spent 150 hours recording Rüppell's vultures at two colonies, one at Diergaarde Blijdorp in Rotterdam and the other at Avifauna in Alphen aan den Rijn. Because eggs at Blijdorp are incubated artificially, the researchers were also able to record the eggs and chicks there. In total, they collected 2,500 "vocalizations," sounds produced by the birds' vocal organs.
The researchers analyzed each sound individually, measuring its duration and pitch and counting the number of distinct "syllables" or notes it contained. This allowed Proudfoot and his colleagues to identify 16 different call types. Notably, some calls were clearly distinct, while others blended into one another.
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