Songbirds without a song

What’s a songbird without its song? Sadly, we are finding out.

Australian regent honeyeaters are failing to learn their species’ tune due to dwindling populations, according to a study published in the journal Proceedings of the Royal Society B, and this is thwarting the male birds’ ability to attract females.

Like humans and other species, young songbirds need to learn their culture’s way of communicating. But researchers from the Australian National University (ANU) discovered that the critically endangered birds (Anthochaera phrygia) are losing opportunities to learn from their own kind, with spiralling ramifications for their survival.

“The fact that regent honeyeaters are losing their ability to sing is a warning sign that the species is on the very brink of extinction,” says lead author, ecologist Ross Crates from ANU.

“Since females prefer males who sing properly, it could create a vicious cycle where females breed less, few young fledge, there are fewer adults for young to learn from, and so on.”

The study arose from efforts to try and conserve the species, who are in freefall due to habitat destruction. Because they’re so sparse the team set up a vast monitoring program throughout their range from northern Victoria to southern Queensland.

That’s when they found something unusual.

“Very early on we noticed some males were singing like other species,” says Crates, “so we decided to keep notes on the songs of every male we found, get recordings of their song, and keep track of their breeding success.

“So this study is the result of five years hard work searching far and wide for these birds that are essentially needles in haystacks!”

The Difficult Bird Research Group surveyed 1300 monitoring sites. When birds were found, their song was recorded and they were followed closely to see if they were paired to a female – and if so, if their nests were successful.

The team also recorded birds bred in captivity for release into the wild, and dug up old soundtracks of the species from 1986 to 2011. Then they analysed all the songs, mapping them over space and time.

In places with bigger populations such as the Blue Mountains, males sang rich, complex tunes. But some young males without their elders around were singing simpler songs or even incorrect tunes of other species. And, much like human dialects from England to the Scottish Highlands, birds down south sang different songs to their brethren up north.

Importantly, captive birds sang completely different songs to wild birds, suggesting they would struggle to mate with their brood when released. This was confirmed by observations that females paired and nested less often with males who sang unusual tunes.

It’s not all bad news – the researchers are now teaching young males in captivity by playing them recordings of birds that sing well, in an attempt to boost their chance of breeding with their kin in the wild.

The findings have lessons for conservation initiatives more broadly, says Crates: “Our study emphasises how important it is for conservation programs to think of ways they can help endangered species to maintain important cultural traits like songs.”

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Further reading:

• Aussie Backyard Bird Count takes flight
• Bird genome project really takes off
• Bird mating habits challenge evolution

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