A critically endangered songbird, the regent honeyeater, used to roam from Rockhampton to Adelaide in large numbers, but it is estimated fewer than 300 remain in the wild.
If nothing is done to stop their demise, scientists predict the species will become extinct within less than 20 years.
That would make it only the second bird in Australia to become extinct since European colonisation.
But researchers from the Australian National University are hopeful that will not be the case.
The once-common striking yellow and black bird is now only found in three small areas: the New South Wales Central West, near the Blue Mountains, on the Northern Tablelands and in northern Victoria.
Professor Heinsohn has spent years finding answers to the question — how can they be saved from the brink of extinction?
"They're one of the most difficult species to study, to monitor and therefore to protect," he said.
A losing battle
The regent honeyeaters' habitat has been subject to land clearing, prolonged drought and is prone to bushfires.
It is understood 90 per cent of their preferred woodlands have been destroyed.
The species once thrived on living in large flocks to fight other birds for food — today they are losing the battle for nectar.
"When there used to be a lot of them, they were one of the major pollinators of a range of eucalyptus trees," he said.
Professor Heinsohn fears, without that pollination service, more forest will be lost.
On top of all of that, their breeding success has drastically fallen because their nests are being raided by aggressive species, such as the noisy miner.
A change of tune
The solution, according to Professor Heinsohn, is to better protects nests in the wild by controlling predators, release more zoo-raised birds and, most importantly, restore their habitat.
Birdlife Australia and the Taronga Conservation Society have been breeding the birds in captivity to try to bolster the wild flock sizes, along with planting trees and guarding nests.
The conservation program has simply slowed their decline rather than stopping it altogether.
All efforts, according to the study, must be ramped up significantly if the species is to have a fighting chance of survival.
At least 100 birds would need to be released every two years for two decades to keep the population above the extinction threshold.
The task is further complicated, with females in the wild having been found to reject zoo-bred males because their songs are different.
Staff at Taronga have even begun tutoring the young males in song by playing them recordings of males not in captivity.
Professor Heinsohn believes everything else is a lost cause without saving the little habitat that remains and re-establishing that which has been lost.
He said it was important every effort goes into saving any species at risk, but with regent honeyeaters it is particularly vital.
"To have lost that wonder of nature feels really sad to me and also the impact it's going to have on the integrity of our native bushland — I think it's very important we get this particular species back."
The ultimate goal is to see the regent honeyeater become self-sustaining and roam the nation's east coast in tens of thousands yet again.
