You can’t teach an adult bird a new tune. Or can you?
New research proves that wild Savannah Sparrows can learn to sing different melodies at two ages, shedding light on critical learning periods for songbirds. Previously only seen in laboratory settings, this is the first experimental study to show the behavior in wild subjects.
A team of researchers, led by Dan Mennill, a professor at the University of Windsor, spent six years banding and monitoring a population of Savannah Sparrows on Kent Island in New Brunswick, Canada. Over five generations, they consistently saw that males that came back to the isle to breed as adults were able to pick up new songs belonging to distant Savannah Sparrow populations. Not only that, a few subjects even passed the notes on to younger birds in the locale. The results were published in Current Biology last week.
Savannah Sparrows, which are found in grasslands and coastal habitats across North America, sing slightly varied tunes depending on their location. Mennill’s team took songs recorded on the West Coast and broadcast them to Kent Island birds on the East Coast. In all, 30 male sparrows learned the new songs during the experiment, and of those, four individuals passed on what they learned to others on the island, revealing two generations of vocal learning.
Three male Savannah Sparrows singing the typical Kent Island song:
Three male Savannah Sparrows singing West Coast songs:
Vocal learning occurs when animals echo fresh sounds or modify existing ones based on what they hear in their environment. Songbirds and humans are among the few groups that exhibit this behavior. (Hummingbirds, parrots, and cetaceans are other examples, and increasing evidence points to bats being vocal learners as well.) This is opposed to creatures like dogs, whose vocalizations are genetically coded and inherent at birth.
In addition to confirming that Savannah Sparrows fit the songbird mold, Mennill and his team discovered that there are two phases of life crucial to driving the behavior in the species: the early months of the sparrow’s first year of life, and then the onset of adulthood, when males are coming back to their nest sites to breed. The second period is especially formative, because it helps shape the bird’s anthem for the long run. “They hear many types of sounds when they're young,” Mennill says. “If they’re re-exposed to those sounds when establishing their first breeding territory and that triggers this learning, that means those are the songs they sing for the rest of their lives,” Mennill says.
Trying a new tune didn't seem to affect these sparrows' chances at romance, however. Mennill says that all but one of the complying Kent Island subjects attracted a mate by belting the West Coast variation, and they found no evidence of the birds being limited by experimental songs.
While the results are clear cut, the set up had its challenges, Ryan Norris, a professor at the University of Guelph and coauthor on the study, says. The team didn’t know if a singing class in the wild would have the same impact as in a lab setting.
“The environment is noisy, and social interactions between wild animals introduce a bit of chaos,” Mennill adds. “So, finding the [sparrows] on their territory and pointing a microphone on them is a challenge. But it’s one that we’re quite good at.”
Using the right sound system proved to be a key element. The scientists chose programmable, solar-powered speakers that only played during the day to mimic real bird behavior and create optimal learning conditions.
The team now plans to track the birds that incorporated experimental songs to see if they start a trend across the broader population. Maybe this is how sparrow pop stars are made.
Correction: The article previously stated that Savannah Sparrows were learning the experimental songs at different stages in life. In fact, the capability was seen at two ages, both of which were in the earlier part of development. The story was also modified to specify that this is the first time scientists have experimentally studied this behavior in wild animals. Finally, there was a misquote of “microscope” instead of “microphone.”