Researchers say they have discovered one of Australia’s most endangered birds in forest in Tasmania, outside its previously known habitat.

Scientists from the Australian National University say the find is a rare piece of positive news for the King Island brown thornbill, which was last year ranked as the Australian bird most likely to go extinct within 20 years if nothing was done to secure its survival.

Researchers doing surveys on the island say they have found the small brown bird in a patch of forest on private land several kilometres outside of its known range in the Pegarah state forest.

The research team from ANU, BirdLife Australia, the Tasmanian government and the Cradle Coast natural resource management had been conducting the first large-scale survey of the island for both the thornbill and the King Island scrubtit.

The King Island scrubtit is another critically endangered bird that was believed to have fewer than 50 individuals remaining in the wild.

Using a new technique that involved repeated surveys of patches of habitat in five-minute bursts, the team was able to photograph and capture audio recordings of the animals.

Lead researcher Matt Webb, a conservation scientist at the ANU, said they had found thornbills at more than 20 sites and scrubtits at more than 60 sites.

“This is a little bit of positive news but the reality is these birds are still two of Australia’s birds most likely to go extinct in the next 20 years,” Webb said. “Securing these two birds is beginning to look like it just might be possible, particularly if strong commitments are made by government and other land managers.”

The scientists have further data analysis to complete – and it is possible some birds were recorded more than once at different locations – but Webb estimated they had records of 30 to 50 thornbills and up to 70 scrubtits.

He said all of the areas where they identified thornbills had mature eucalypts present, often in tiny patches of forest where they haven’t been cleared on the island.

Webb said the case was similar for the scrubtit, which had been pushed into small areas of remaining habitat.

He said it showed the importance of habitat protection for the animals, because “even the loss of small areas, a hectare here or a hectare there, can be devastating for them”.

Jenny Lau, of BirdLife Australia, said the surveys could help conservation workers and volunteers target the right places.

Last year, the King Island community called for urgent federal help to try to prevent the birds from going extinct.

“These birds are part of King Island’s unique natural heritage and we are thrilled we’ve discovered a new, efficient way to find them,” Lau said.

Anna Wind, the coastal coordinator for Cradle Coast natural resource management, said the discovery of the thornbill outside of the one forest patch it was thought to be confined to was a “breakthrough”.

“The number of sites where the species were detected has given cause for hope that populations of both species are larger than previously thought,” she said.