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In the half century since the Argentine parrot arrived in Europe and spread throughout the continent, the species has developed different dialects that vary according to countries and cities.
Scientists from the Max Planck Institutes for Animal Behavior and Evolutionary Anthropology compared the calls made by these birds — whose name is Myiopsitta monachus — in eight cities in four European countries and found that these parrots now "sound" different in each city. The work is published in the journal Behavioral Ecology.
"Like humans, Argentine parrots in Europe have unique ways of communicating depending on where they live," lead author Stephen Tyndel, a doctoral student at the Max Planck Institute for Animal Behavior, said in a statement.
Europe does not have any native parrot species. However, several species, including the monk parrot, have established populations after some individuals escaped the pet trade. Native to South America, Argentine parakeets or monk parakeets now exist in large numbers in several countries in Europe.
Like all parrots, these birds have an exceptionally flexible vocal repertoire and can imitate and learn new sounds throughout their lives. Because the invasive parrot recently spread across Europe, Tyndel says, "Argentine parrots are the perfect test tube for studying how complex communication evolves in a species other than our own."
To find out whether these birds in Europe developed dialects, that is, calls that differ depending on where individuals live, the researchers recorded Argentine parrots in eight cities in Spain, Belgium, Italy and Greece. A novel statistical method allowed them to test whether parrot calls were different from city to city, and also whether calls were different between parks within the same city. "We wanted to know not only if different dialects exist, but also at what geographic scale they are found," Tyndel says.
They found that parrots did have different dialects in each city. In Brussels, for example, they had contact calls that were particularly different from those in other cities, says co-lead author Simeon Smeele, a scientist affiliated with the Max Planck Institute for Animal Behavior and the Max Planck Institute for Evolutionary Anthropology.
For the most part, the dialects differed in the frequency modulation structure within each call, "which is very difficult for humans to hear," Smeele adds.
But when the scientists looked for dialects within each city's parks, they found no differences. Parrots didn't have unique calls from park to park. "Taken together, this suggests that parrot dialects diverged early when birds invaded European cities, but then did not change significantly during this period," Tyndel says.
The results were surprising, Tyndel says. "This suggests that dialects arose through a passive process (birds copying birds make small mistakes, and therefore cities slowly become different from each other) or that they were different to begin with and that these differences persisted over time."
But the team hasn't ruled out that dialects could also be formed by an active process that could help birds with social communication, such as recognizing group mates. In parks, Argentine parrots live in tightly packed nests. The researchers believe there could be vocal differences, such as slang, in these smaller social units.
"We think dialects could be used to communicate who is part of which nest group, like a password," Smeele says. In the future, the team plans to find out how individuals learn from each other and whether smaller groups display dialects within the parks.
"This will contribute to our understanding of parrot communication," says Tyndel, "and provide insight into the ways in which complex communication is linked to the complex social lives of humans and animals."