New research shows young magpies learn how to turn basic sounds into complex calls and sequences in much the same way human children learn to turn sounds into words and words into sentences.
The study, published in the journal Proceedings of the Royal Society B, provides the first evidence of learned syntax in any non-human animal.
In a project led by Dr Stephanie Mason from the Centre for Evolutionary Biology at The University of Western Australia, researchers followed 11 fledgling WA magpies for 200 days from the time they left the nest at the age of three-to-four weeks.
Each fledgling was recorded for an hour at a time at weekly intervals for the first 100 days – the main period of vocal learning – and then once every three weeks for another 100 days, to track how and when they developed their vocal repertoire.
“Magpies aren’t born knowing complex call sequences,” Dr Mason said. “Rather, here we show they appear to start life with basic in-built calls and develop more sophisticated call sequences through social exposure.
“Similarly to the way human toddlers learn sounds, words and then sentences, magpies initially make small, simple sounds and then learn from others in their social group how to combine these building blocks into meaningful sequences.”
The researchers found social connection was a key factor in how quickly and effectively individual fledglings learned.
“Previously it’s been shown in various species that simply being part of a larger group leads to more complex communication, but what we saw in the magpies was more nuanced,” Dr Mason said.
“Fledglings from the same social group showed drastically different trajectories depending on how many of their group members they interacted closely with and for how much time.
“The more social the fledgling, the more vocally sophisticated it became.”
Dr Mason said syntax – the ability to communicate infinite ideas by combining sounds into words and words into sentences – had traditionally been seen as unique to human language.
However, recent research had found several primate species and the Western Australian magpie produced complex call sequences that parallelled sentence-like structure.
“The major difference is primates seem to lack the capacity to learn new sounds, whereas magpies are open-ended vocal learners,” Dr Mason said.
“This means that, like us, they’re able to learn new sounds indefinitely throughout life – something we see in their capacity to mimic new sounds in their environment.”
Dr Mason said what hadn’t been known was how magpies learned to produce their sophisticated call sequences.
“This is the first study to capture the emergence of call sequences over the course of development in any non-human animal,” she said.
“It provides the first evidence of learned sequencing of calls outside of humans, with fledglings learning the specific sequences of their social group.
“These sequences were all made up of the same building block calls regardless of social group, suggesting it may not be the calls themselves that are learned, but the way they are combined.
“It’s a bit like learning the specific ‘grammar’ or dialect of the community in which you grow up.”
Dr Mason said it still wasn’t clear why different social groups needed to have such different sequence repertoires, given they shared the same underlying calls.
“What is the function of these group-specific ‘dialects’?
“This is possibly the most interesting and baffling question that remains about magpie communication.”
Dr Mason said while this was the first study to capture this kind of learning and complexity in a non-human, open-ended vocal-learning animal, it was likely to apply to a much broader range of species than there was currently evidence for.
“Further studies of this kind, that document the emerging repertoire over time and individual-level vocal and social data, are crucial to understand what drives the variation and thus evolution of communicative complexity,” she said.