An associate professor at the UTRGV College of Sciences is continuing to discover new data on parrot vocalization that is similar to human babbling.
Associate Professor for the UTRGV Department of Biology and School of Earth, Environmental and Marine Sciences Karl Berg is leading the research project in Venezuela. Berg learned wild green-rumped parrotlets engage in vocal babbling similar to human infants.
His inspiration to study vocal babbling began almost 20 years ago when he was doing his doctoral dissertation research on parrot populations in Venezuela. He said he began recording inside nest cavities to study nestlings’ vocal development, and discovered they learn contact calls from their parents, functioning like individual names.
As Berg was walking through the field site in Venezuela, he said he found a field assistant recording inside the nest box. She was listening through headphones, and when he asked if the parents were inside, she said “no.”
Since Berg was primarily recording parent-offspring interactions at the time, he asked to take a listen and heard a bird calling persistently.
“And I asked her again, I said, ‘Are you sure the parents aren’t inside there?” he said. “And she said, ‘No.’ And she showed me the video and it was just nestlings inside there. And that’s kind of when it dawned on me that we had just uncovered the vocal babbling stage. That was pretty exciting.”
Berg said he collected 15,000 hours of parrot babbling. He said unlike songbirds, both male and female parrots babble equally, which aligns their vocal behaviors more closely with human vocal learning.
Berg added researchers have studied songbird babbling for 50 years, focusing on how sex steroids shape the male brain for lifelong singing, as males typically sing for mating and territory defense. However, the hormone-driven model contrasts with human babbling, where sex steroids play little role.
According to Berg, human babbling starts around six months and ends by 12 months, long before reproduction is relevant. Instead of sex steroids, the stress hormone corticosterone, which aids development and learning, may play a role. In parrots, Berg confirmed they produce this hormone early on and then tested its effects by giving small doses to select individuals of both sexes.
“And we were able to show that it increased the size of their babbling repertoires,” he said. “And so, we kind of took that as a sign that the hormone is sort of serving a useful function. It’s helping them learn the repertoire of the parents.”
Berg said parrots are unusual among birds because their siblings have significantly staggered ages. In many species, this often leads to the oldest killing the younger ones to eliminate competition.
However, his 15,000 hours of nest recordings show that, instead of harming each other, parrot siblings cooperate. Berg said this supports the idea that sibling hierarchies may have played a role in the emergence of human language, where older siblings help rather than eliminate the younger ones.
“But an alternative tactic would be to help mom and dad out,” he said. “Help raise, help care for the younger nestlings and score points with mom and dad at the same time could be an effective alternative strategy.”
Despite the importance of human language, Berg said the heritability of babbling remains unknown. He added ecologists assess traits by examining their impact on longevity, considering whether a complex babbling repertoire in infants correlates with a longer life.
“So, that’s one thing that I think is really important that will help us start to understand the behaviors and importance,” Berg said. “So, it might enable individuals to sort of function in a lot of different contexts for example. It almost certainly is a process where the brain is [becoming] better connected and socialized so that they can navigate wild societies and individuals and so forth.”
His work has gained recognition and is even featured in prominent publications such as NPR, Science, Forbes and Psychology Today.
This is Victoria Gonzalez for Vaquero Radio.
