Regent honeyeaters have ditched their typical tune for a shorter, simpler song. Why?

New generations of regent honeyeaters are singing a shorter song, replacing the bird’s typical tune which can no longer be heard in the Blue Mountains.

Since 2020, a rapid shift in song culture has accompanied a significant decline in the critically endangered bird’s population, according to research in Royal Society Open Science.

Daniel Appleby, an Australian National University researcher and the first author of the paper, said the typical song for the Blue Mountains birds had “basically disappeared from the wild entirely” as a simpler version, containing half the number of syllables, had become the cultural norm.

ANU researchers tracked and classified the calls of wild regent honeyeaters and their success at pairing and nesting between 2020 and 2022, continuing previous data collected between 2015 and 2019 that indicated some male birds were singing a clipped version of their typical song.

The share of regent honeyeaters singing the clipped version increased from 5% in 2015 to 91% in 2022 in males with known song type, the research found. Those singing the more complex, typical version declined from 73% in 2015 to 5% after 2020, with no birds singing the typical song in 2022.

Appleby said the versions sounded similar – “a metallic, almost bell-like song” – but the new song was an abbreviated and simplified take.

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Bird songs could change naturally over time, he said, due to “copying errors” and “cultural evolution”. Simplification was unusual, and probably related to population decline and fewer opportunities for young birds to learn from adult tutors.

In three decades, the population of the striking black bird with gold speckling has declined from 1,500 to fewer than 300, with habitat loss the key threat to the bird’s survival.

The ecologist Dr Joy Tripovich, who researches regent honeyeaters at both the Taronga Conservation Society and the University of New South Wales and was not an author of the new study, said song was important to the survival of the critically endangered species.

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“We believe song is important for courtship between males and females in terms of social cohesion, keeping the birds together, and for feeding as well as for foraging,” she said.

Researchers were initially concerned that birds singing the shorter version had a lower likelihood of successfully nesting and pairing. As the clipped song became the cultural norm, females became more accepting of the males singing it, the study found, although breeding success never returned to the best rates recorded from 2015 to 2019.

“If you’re trying to attract a female mate, song has a big function in that. It’s not just how elaborate the song is, but quite often, how familiar that song is,” Appleby said.