The regent honeyeater, found in wooded areas south-eastern Australia, is now listed as critically endangered with habit loss the primary driver of its decline.
Recent research by ecologists from the Australian National University found remaining regent honeyeaters were losing their rich repertoire of songs as populations fall.
Like children learning to speak, many bird species learn their songs by associating with adults.
But the honeyeater is at risk of losing its vocabulary as adult birds become increasingly rare.
Their chances of reproductive success also tumble if they are unable to sing songs that are not impressive enough to attract a mate.
The team is now trying to teach birds bred in captivity the symphonies of their wild counterparts by playing them audio recordings so they have more chance of finding a partner upon release.
Lead author Dr Ross Crates said: “If endangered birds are unable to learn how to sing correctly, it seriously impacts their ability to communicate.”
He added: “It could also be exacerbating the honeyeater’s population decline, because we know a sexy song increases the odds of reproduction in songbirds.
“Females will avoid males that sing unusual songs.”
The researchers found that in regions where populations were slightly higher, the males sang richer and more complex songs.
But in areas where numbers were in steep decline, the males were singing simplified or “totally incorrect” songs.
Co-author of the study Dr Dejan Stojanovic said: “For example, 18 male regent honeyeaters, or around 12% of the total population, were only able to copy the songs of other bird species.
“This lack of ability to communicate with their own species is unprecedented in a wild animal.
“We can assume that regent honeyeaters are now so rare that some young males never find an older male teacher.”
The findings also spell trouble for regent honeyeaters bred in captivity, who were found to have totally different songs to wild birds.
It could hamper conservation efforts, as the captive birds may be less attractive to wild birds once they are released.
“The unusual songs of captive-bred birds could reduce their attractiveness to wild birds when they are eventually released,” Dr Crates said.
He continued: “So we’ve devised a new strategy to teach young captive regent honeyeaters to sing the same song as the wild birds by playing them audio recordings.
“Loss of song culture is a major warning sign the regent honeyeater is on the brink of extinction and we still have a lot to learn about how to help them.”
The study will be published in the journal Proceedings Of The Royal Society B.