The critically endangered masked owl has been sighted within the Barrington Wildlife Sanctuary for the first time in more than a decade.
Conservation organisation Aussie Ark is "over the moon" with the discovery, which managing director Tim Faulkner labelled "big news".
"Aussie Ark has been conducting nocturnal surveys in the Barrington Wildlife Sanctuary for 13 years and this is the first ever time we've seen these owls," Mr Faulkner said.
"To have them turn up in the Barrington Wildlife Sanctuary means we're doing something right. It's proof of a healthy ecosystem."
The heart-faced owl is endangered throughout its range and heavily impacted by lack of food, destruction of habitat and nest sites, and the ingestion of poison bait.
The second-largest nocturnal bird in Australia after the powerful owls, with the females - which are the larger of the genders - weighing up to 1.2kgs.
Mr Faulker made the discovery while on a survey with US partners Re:wild, with photographer Barney Long taking five photographs that confirmed the elusive bird's identity.
The main food sources of the Masked Owl are bush rats, swamp rats, antechinus, and bandicoots.
Mr Faulker said all those species naturally occur in the Sanctuary and are thriving thanks to the Sanctuary's feral-proof protection, offering the owls a wonderful smorgasbord and encouraging them to stay.
"While Aussie Ark has a range of rewilding projects for locally extinct species, the species that still existed there in really low numbers have also bounced back and that's encouraged the owls into the sanctuary," he said.
"Now that they're there, we want to know more. We'll be working with Birdlife Australia over the next couple of months to confirm numbers and see if they're breeding. Hopefully we'll be able to locate nest sites."
Aussie Ark recently several greater gliders had voluntarily taken up residence in the 400-hectare feral-proof Barrington Wildlife Sanctuary.
In December, the conservation organisation released 20 threatened parma wallabies in to the sanctuary.
