Once abundant, the glossy black cockatoo is being wiped out across eastern Australia with one of its remaining habitats south of Sydney under threat from development.

Experts say the glossy blacks are doing it tough and without community support they will not survive.

The native birds are endangered across Australia, from central Queensland to East Gippsland in Victoria.

They're listed as vulnerable in New South Wales.

Those documenting the elusive bird's decline say it is being driven by land clearing and the disappearance of their homes and only food source.

The Great Western Wildlife Corridor is the only remaining vegetated habitat for the birds between the Blue Mountains and Morton National Park in the Southern Highlands.

"It's really important we optimally manage their habitat,'' said Matt Cameron, threatened species officer with the Office Environment and Heritage.

"If we do develop land, then we do it in a sensitive way — protecting large, old trees and foraging habitat. Then the glossies have a future."

A pair of female and male glossy black cockatoos in the wild. ( ABC News )

Louise Docker, a landholder from Penrose in the NSW Southern Highlands, is helping to manage the birds' habitat.

"Everything south of Sydney is being knocked down and developed and it's really important to keep those trees where the cockatoos nest when they're breeding," Ms Docker said.

"I'm just passionate about wildlife and love birds, we have a lot of around here and I want to make sure that they don't disappear.

"If we don't do something about them they may not be around in a few years' time."

Ms Docker has signed up to the Glossies in the Mist project and is regenerating 12 acres of her Southern Highlands property at Penrose with native sheoak trees.

The Glossies in the Mist project involves private landowners reporting glossy black-cockatoo sightings, mapping stands of Allocasuarina and assessing feeding and hollow-bearing trees on their properties and in the local area.

Louise Docker is planting 80 sheoak trees on her Southern Highlands property to attract glossy black cockatoos. ( ABC Illawarra: Chloe Hart )

"They rely on large hollows for nesting which are now really rare and vulnerable to things like clearing for firewood or bushfire hazard reduction burns," said Mr Cameron.

The birds can live up to 35 years of age in the wild and up to 50 in captivity.

But feeding solely on sheoak cones makes them vulnerable once their habitat is destroyed.

"Glossies have evolved a specially-adapted bill that allows them to apply both massive force to the cones to open it, but then undertake these really dexterous movements to actually husk the seed and ingest the kernel," Mr Cameron said.

Simon Tedder, Glossies in the Mist project leader with the OEH, said the group was trying to retain hollow-bearing trees and Allocasuarina species or sheoaks.

"We are hoping residents can act like citizen scientists and report glossy black cockatoos sightings and by observing their she-oak stands for crushed cones," Mr Tedder said.

Glossy black cockatoos only feed off the seeds of the Allocasuarina she-oak cones. ( ABC Illawarra: Chloe Hart )

"They can retain those sheoaks and report hollow-bearing trees and preserve the glossy black cockatoo habitat in this region."

It's hard to know how many of the evasive birds remain in the wild.

They are smaller and have quieter calls, unlike the yellow tails or the sulphur-crested cockatoos.

They also just live in pairs with their young, rather than large flocks.

Landholders are trying to help by counting the cockatoos at waterholes where they typically visit at nightfall to drink.

"This project will connect up tenuously-linked populations so smaller populations are connected to each other and can buffer each other from the negative effects, even global warming in future," Mr Cameron said.