Regent honeyeaters were once abundant in the forests of southeastern Australia, congregating in enormous, eye-catching flocks. Today, the black-and-yellow songbirds are critically endangered, with just a few hundred remaining in the wild.
As the birds disappeared from the landscape, so did their distinctive song, a soft, warbling melody that males use to defend territory and attract mates. Instead, some young males adopted the songs of entirely different species. Others produced shorter, simpler versions of the standard song. Honeyeaters born in zoos, as part of a captive breeding program, didn’t learn the tune at all.
Now, scientists are restoring the song by deploying a few skilled honeyeaters to act as vocal tutors. Researchers found that regent honeyeaters that knew the standard song successfully taught it to young, captive-born birds before they were released into the wild. Some of these avian students even learned the song well enough to teach it to the next generation, the researchers wrote last month in Scientific Reports.
Although more research is required, the scientists hope that the tutoring program, which is ongoing, might help boost reproductive rates in the wild and, perhaps, get the world’s last remaining honeyeaters all singing the same tune again.
“The traditional song has some sort of intrinsic value to it, but it’s also really important for the birds to have a stable song,” said Daniel Appleby, a conservation biologist at Australian National University and an author of the study. “The song is pretty critical to their reproduction.”
The study also reflects a growing understanding of the importance of animal culture — and a recognition that successful conservation programs may need to find ways to preserve socially learned behaviors like birdsong.
“As captive breeding for conservation and reintroduction is increasingly relied upon for the survival of species, we really do need to consider culture,” Dr. Appleby said.
The regent honeyeater population dropped sharply over the 20th century, as the birds’ woodland habitats were cleared. Today, scientists estimate, roughly 250 wild birds live in the fragmented forests of southeastern Australia, spread across an area about the size of Spain.
“So studying them is a nightmare, as you can imagine,” said Dr. Appleby, who is part of a research lab aptly named the Difficult Bird Research Group.
This low population density may also explain why the honeyeater song began to change. Young birds typically learn the tune by listening to and observing adult males, but fewer birds on the landscape meant fewer learning opportunities.
A parallel problem emerged in the captive breeding program, where young birds often had little exposure to adult males during their critical song-learning period. When these zoo-born birds were released into the wild, they sang “strange, rudimentary songs,” Dr. Appleby said, and relatively few managed to find wild mates.
So Dr. Appleby and his colleagues decided to try teaching the wild song to the captive-born birds at the Taronga Zoo and Taronga Western Plains Zoo. Over several years, they experimented with a variety of strategies.
They housed some young birds in aviaries with speakers, which played recordings of the wild song from sunrise to sunset. “That just completely failed,” Dr. Appleby said. “We didn’t notice any difference in the birds.”
But other young birds got real-life tutors: two wild-born males who sang the traditional honeyeater song. When the young chicks lived alongside these tutors — first in a neighboring aviary and then in a shared one — they began to sing their tune.
“Three months in, we started hearing our first little renditions of a traditional wild song,” Dr. Appleby said.
To get good results, the scientists found, they had to keep class sizes small, with no more than five avian pupils per tutor. In these small groups, many tutored birds produced songs that were essentially indistinguishable from the traditional wild song.
“Those birds produced very, very good songs — so good that in the following year, those birds became tutors themselves,” Dr. Appleby said.
Their students, in turn, also learned the wild song.
“It does seem to be that they could continue doing this for multiple generations in the same way, without too many problems, which is great,” said Rebecca Lewis, a conservation scientist at Chester Zoo in England, who was not involved in the study. “It’s a sustainable method.”
Indeed, the tutoring program is continuing. The researchers are planning to keep a close eye on the tutored birds to determine how they fare in the wild and whether the traditional song spreads as wild-born chicks eavesdrop on their songs.
But the study demonstrates that it is feasible for captive breeding programs to take concrete steps to preserve the culture of threatened species, said Peter McGregor, an expert on animal communication and birdsong at ISPA – University Institute in Portugal, who was not involved in the study.
“They’ve done the hard work of actually doing this stuff with captive populations,” he said. “It’s becoming more and more clear that quite a lot of critical aspects of animals’ survival and reproduction is socially learned.”
Emily Anthes is a science reporter, writing primarily about animal health and science. She also covered the coronavirus pandemic.
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