The Argentine parrot (Myiopsitta monachus), a species of the Psittacidae family, has become an invasive species and a nuisance in many regions far from its native territory in Argentina, Brazil, Bolivia, Uruguay, and Paraguay. Barcelona exemplifies the adaptive capacity of these bright green parakeets with their noisy activities. While neighbors and tourists perceive the sounds of Argentine parrots (similar to the closely related, though different in origin, Kramer’s parrots, Psittacula krameri) as noises, experts, from a scientific perspective, categorize them as songs, calls, and vocalizations emitted by these birds.
Data on the presence of wild Argentine parrots in Barcelona dates back nearly 50 years, and over the last two decades, a monitoring program led by the Museum of Natural Sciences of Barcelona has been marking and tracking the individual behavior of around 3,000 of these birds.
Barcelona’s experience forms the basis of a study led by experts from the Max Planck Institute of Animal Behavior in Radolfzell (Germany) and the Museum of Natural Sciences of Barcelona. For the first time, they present evidence that individuals of this species have a unique vocal tone, known as a vocal fingerprint, similar (with differences) to that of humans. «This finding in a wild parrot raises the possibility that a voiceprint may also be present in other vocally flexible species, such as dolphins and bats,» state the authors in an article presenting their results published in the Royal Society Open Science journal.
Similarities and Differences with Humans
Humans have complex and flexible vocal repertoires, yet they can recognize each other solely by voice. This is because humans have a vocal fingerprint: our vocal tract leaves a unique signature in the tone of our voice in everything we say, explain the authors in a joint statement released by the Max Planck Institute and the Museum of Natural Sciences.
Other social animals also use vocal signals for recognition. In birds, bats, and dolphins, for example, individuals have a unique «signature call» that makes them identifiable to group members. However, these signature calls encode identity in a single type of call. To date, there is little evidence that animals have unique signatures underlying all calls made by an individual. In other words, almost no animal has a vocal fingerprint.
The absence of data on these vocal fingerprints in other species surprised Simeon Q. Smeele, who had already initiated studies on communicative abilities in various species. Among the data preceding his specific study with parrots in Barcelona, Smeele recalls that, in previous studies, it has been found that parrots, much like humans, use their tongue and mouth to modulate calls, meaning that «their squawks and screams sound much more human than the clean whistle of a songbird.»
Additionally, like humans, parrots live in large groups with diverse and changing members. «There could be dozens of birds vocalizing at the same time,» he asserts. «They need a way to keep track of which individual is making which sound.»
Visiting Barcelona and Its Parrots
Smeele wondered if parrots, possessing the right anatomy along with the need to navigate complex social lives, could have also evolved vocal fingerprints. To find out, he traveled to Barcelona, where the largest population of individually marked parrots exists in the wild. Argentine parrots (Myiopsitta monachus) roam parks and gardens in flocks of hundreds of birds, and the monitoring program led by the Museum of Natural Sciences of Barcelona has valuable data on them.
Armed with shotgun microphones, Smeele and his colleagues recorded the calls of hundreds of individuals, collecting 5,599 vocalizations, including 3,203 contact calls, 185 tja calls, 265 trruup calls, 249 alarm calls, and 364 growls. This makes it the largest study of individually marked wild parrots to date. Importantly, Smeele re-recorded the same individuals over two years, revealing how stable the calls were over time.
They then used a set of models to determine how recognizable individuals were within each of the five main types of calls made by this species. Surprisingly, they found a great variability in the «contact call» used by birds to convey their identity. This contradicted a long-standing assumption that contact calls contain a stable individual signal and suggested that parakeets are using something else for individual recognition.
Continuing the Research
The Barcelona team would complement future experiments and analyses with an ecological study, tagging parrots with GPS devices to determine how many individuals overlap in their roaming areas.
«This can provide information on the remarkable ability of the species to discriminate between calls from different individuals,» says Juan Carlos Senar from the Museum of Natural Sciences of Barcelona.
And if it turns out that parrots do have a true vocal fingerprint, Smeele believes this would provide an answer to how these birds can be vocally flexible and sociable at the same time. The implications would also extend beyond parrots: «I hope this finding prompts more work to discover voiceprints in other socially communicative animals, such as dolphins and bats,» highlights the lead author of this study on animal behavior.