Just like humans, young songbirds are thought to learn their vocalizations by listening to adults — a process that has been studied in the laboratory but never experimentally in the wild, until now.
A new investigation, published Thursday in Current Biology, demonstrates that wild birds learn to sing based on sounds they hear in the first year of their life.
“This research is the first direct experimental demonstration of vocal learning in wild birds,” said UWindsor biology professor Dan Mennill, lead author of the study.
“We used loudspeakers to simulate the voices of wild birds, and we broadcast songs with distinctive acoustic features to five generations of birds. We found that young savannah sparrows learned the distinctive songs from the loudspeakers, demonstrating the phenomenon of vocal learning in wild animals.”
During the course of a six-year field study, 30 birds learned songs that matched the experimental vocal tutors.
“In addition to the 30 birds that learned songs from the loudspeakers, in four cases birds passed the experimental songs on to other birds” Dr. Mennill said. “This reveals two generations of vocal learning.”
The research, conducted on eastern Canada’s Kent Island at the Bowdoin Scientific Station, was on a long-studied population of savannah sparrows.
“We have been studying savannah sparrows on Kent Island for many generations, and we know that many birds born on this island return to breed here as adults,” said Ryan Norris, a University of Guelph professor and a co-author on the study. “This presented us with a special opportunity to manipulate the early acoustic environment of young sparrows, and then study the voices of those same animals when they returned from migration as adults.”
In a second part of the experiment, the researchers varied the time of year when different experimental songs were played through the loudspeakers.
“We found that birds need to hear a song not only in the first months of their lives, but also when they returned from migration the following spring,” said Mennill. “This reveals that there are two critical stages for vocal learning: exposure to adult sounds early in life, followed by re-exposure at the onset of adulthood.”
The collaborative project was funded by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) and involved research teams from the University of Windsor, the University of Guelph, and Williams College.
“This research presents a new technique that can be used to study vocal learning in wild animals,” Mennill said. “Importantly, this investigation confirms that the conclusions of decades of findings from laboratory experiments hold true in the wild.”