Fifteen critically endangered plains-wanderers have been released in south-west New South Wales, despite some birds from the last flock released being killed or going missing.
It is estimated there are fewer than 1,000 left in the wild because of predation and climate change.
In March, 10 zoo-bred plains-wanderers were released into native grassland near Hay as part of a conservation effort to save the birds from extinction.
It followed extensive fox baiting and shooting of cats in the area.
David Parker, a senior threatened species officer from the State Department of Planning and Environment, said of those 10, four died, three dropped their trackers and had not yet been found, and only three were monitored to the end of the 12-week trial.
"They dropped their trackers, we weren't able to follow them to see where they went to but we presume they may be alive," he said.
Of the three that survived the trial, two were last seen paired with wild birds, with hopes there may be chicks.
Mr Parker said casualties in these sorts of programs were "to be expected".
But he also said the research, which was part of the state government's Saving Our Species program, must continue.
"If we pulled up stumps and assumed the worst from those previous releases, we're not going to benefit the bird," he said.
"We need to do a captive program to get this bird out of the hole it is in to improve the numbers in the wild.
"We've got information about the movements, we've got information about their predation, and their survivorship post-release."
Securing the future
For the most recent trial, 15 plains-wanderers have been released into Oolambeyan National Park, a heavily pest-managed area about 500 kilometres south-west of Canberra.
Zoos across Australia are involved in the project.
This time, tiny solar-powered satellite backpacks, with two-year battery lives, have replaced the VHF transmitters, which only last 12 weeks.
Mr Parker said the new technology meant researchers would not have to scour the landscape for days on end with receivers, trying to detect the VHF transmitters.
"We can [now] actually follow the bird's movement from the confines of an office and I can download [location] points of the birds as the satellite passes over and gives us a ping from the transmitter," he said.
He hoped more data could be gathered to help the future protection of the nearly extinct species.
"From doing these releases, we'll learn what we need to do to make sure the birds are happy to go back out to the wild and survive," he said.
The program is expected to last at least another year.
