The next time your pet bird lets out a contact call, it might be saying, "This is me! This is my name!" Researchers call this the parrot’s "vocal signature,” which is the parrot’s unique sound that identifies itself to its flock. This can be seen as the bird’s name, and parrots use this in day-to-day conversation, both in our homes and in the wild.
Courtesy Nick Sly
Researchers studied young green-rumped parrotlets to see how they acquired their contact calls.
But how a parrot acquires its vocal signature was a question that had to be answered. Was it innate; i.e., was the parrot born knowing its vocal signature? Was it taught it? Researchers had always suspected the answer was leaning more toward the latter, and they finally found evidence in the nests of wild green-rumped parrotlets (Forpus passerinus) in Venezuela.
In the article "Vertical Transmission Of Learned Signatures In A Wild Parrot,” published in the Proceedings of The Royal Society of Biological Sciences, researchers found that wild green-rumped parrotlet chicks learned "contact-call templates,” from their parents, according to Karl Berg of Cornell Laboratory of Ornithology in New York.
Each chick appeared to tweak the templates to its own unique sound (or its "vocal signature”) and also gave those contact-call templates to its younger siblings, which seemed to tweak it as well. As a result, individual chicks had their own unique calls. "There were strong differences within a family, which does argue that [individual calls] could be used as vocal signatures,” Berg explained. According to Berg, there were distinct similarities within a family as well.
"The brothers and sisters had contact calls that also had something in common,” Berg said. "It makes sense that, if they’re learning them from the same two parents, there [would] be some similarities. The end result is that the different nestlings’ [vocal signatures] are clearly unique, but it’s sort of like they had the same building blocks to work with. So similarities exist at the family level.”
Berg related this to our own tendencies toward having familial and/or regional influences in the way we speak. "There is probably something in the way we speak that is somewhat unique to our family, our regions, our parents and so forth. Nonetheless, there is something about the way we speak, not just our names, [that] could tie us to our families to some extent.” Berg said.
"We had the same teachers — our parents, grandparents, aunts and uncles — but clearly, early on, our parents are a big influence, along with our siblings. I was certainly influenced by my siblings before influences came from outside the family.”
While some have said this means the parents are naming the chicks, Berg doesn’t believe the research shows that. "We showed that the parrotlet chicks learn their contact calls, which may function like names. They learn these from their parents, but this does not mean the parents ‘name’ their chicks.”
To find out whether the chicks were learning from their parents and siblings (rather than innately knowing the calls) Berg and his research colleagues switched eggs around so that parrotlet parents raised non-biological offspring. As a result, adopted chicks acquired their foster parent’s contact-call templates, supporting the idea that the chicks were learning.
Models For Conservation
Berg, who has worked with several species of parrots in Ecuador and wrote his Master’s thesis on bird vocalization, said this research opens up a whole new field of questions. "Why do they have this? To really get to the answers, we need a lot of different types of studies, [and] we definitely need to know what’s going on in the wild, because this is where these skills evolved over thousands of years. How does this ability help them find food, make friends, figure out who the enemies are, help them raise babies? It has to have some value. We tend to think this ability wouldn’t have come about entirely by chance.”
This group of wild green-rumped parrotlets are the stars of a long-term study that has contributed a wealth of information for scientists and conservation efforts for parrots in the wild for more than 25 years. Steven Beissinger, Professor of Conservation Biology and holder of the A. Starker Leopold Chair in Wildlife Biology at the University of California, Berkeley, set up this study in the low-flat plains called the Llanos, situated north of the Amazon River and near a town called Calabozo.
These parrotlets were prime candidates for the study of wild parrot behavior because of their size, nesting habits and sexual dimorphism. "Most parrots are incredibly hard to study,” Beissinger said. "They travel many miles each day, they nest high in the trees and it’s hard to tell the difference between males and females in certain species. Catching and banding them for study is difficult, too.”
In contrast, green-rumped parrotlets are sexually dimorphic, meaning that males can be visually differentiated from females. The parrotlets nested in hollow fence posts (made from the local wood), not high in the trees. Also, the birds were easy to catch and band, so researchers could identify which was which and the birds they were related to.
Studies on their behavior provide a model for researchers trying to understand the behaviors in other parrot species. The artificial nestboxes that Beissinger made for the parrotlets were the first to be used by any parrot, and the design has since then been scaled to be used for other species
in the wild.
"When I got started, it was a side project for me,” Beissinger said. "Twenty-five years later, it’s produced a lot of interesting information for science and conversation. It’s continued a lot longer than I expected, but it’s been great. Parrots are so interesting.”
For more information about Beissinger’s work, go to his website.
How The Green-Rumped Parrotlets Were Studied
To study how parrotlets acquired their contact calls or vocal signatures, Karl Berg and his group placed video cameras and microphones inside the nests of green-rumped parrotlets. They recorded the sounds the parent parrotlets made to their chicks before the chicks started contact calling (around 22 days of age), and then compared the two. Using spectrographic analysis, they looked at the similarities of calls within a nest, as well as other nests, to see if there were any differences or similarities. The parents had contact calls that were similar to each other, which were similar to the chicks. Among the siblings, the calls were similar to each other.
Parrot communication in the wild from Karl Berg on Vimeo.
Nestling Vocal Signatures from Karl Berg on Vimeo.