But when the birds were not seen in bushland around the NSW Northern Rivers for three months, there were grave fears for the threatened species.

Bushfires and floods have destroyed many of the hollows the glossies call home, along with the casuarina trees they exclusively feed upon.

A trail of clues, in the form for chewed cones, were found in May by bird spotters the Glossie Squad.

The discovery helped grassroots conservation group Glossies Northern Rivers to zero-in on a male and female in bushland near Bogangar, after fruitless searches earlier in the year.

The birds, whose dark feathers hide dazzling red tails, were nicknamed Barry and the Baroness.

"We were trying to keep our cool, but we were jumping up and down with excitement inside," the group's project officer Harry Hackett told AAP.

"It was just magic."

Leonie Valentine from WWF Australia, which supports Glossies Northern Rivers, said the sighting was very reassuring.

"It's one of the real powers of citizen science, when these discoveries are made," Dr Valentine told AAP.

"When they get them after months of looking, it is a eureka moment."

The cockatoos are considered endangered nationally. Their status is vulnerable in NSW, Victoria and Queensland, and endangered in South Australia.

Recent disasters have destroyed more of their food supply and their eucalypt nesting hollows, which were already threatened by land clearing, Dr Valentine said.

"To create those sorts of hollows the trees need to be 100 to 200 years old, so once we've lost those trees from the landscape, it's really hard to replace them," she said.

But there is reason for optimism, with conservationists building artificial hollows and closely monitoring the birds, she said.

An avian expert from the Queensland University of Technology is working with citizen scientists to record the birds' call and trace their movements.

"The glossies are quite an elusive bird. They are not as obvious as some of their their cousins, which are more gregarious and a bit more of a party bird," Dr Valentine said.

"The glossy black really appeal to the introverts."

Ms Hackett said Australia cannot afford to lose the species.

"They're incredible birds," she said.

"It would be a shame if we didn't do everything in our power, on our watch, to help protect and conserve these birds."

Australian Associated Press