Critically endangered parrots that fly between Tasmania and southern mainland Australia each year have had their most successful migration in a decade.
Just 23 orange-bellied parrots, each weighing no more than 50 grams, arrived in the island state's rugged southwest in spring last year.
But that number is expected to more than double in 2020, with 40 of the birds having arrived by early November.
Their population is propped up by a captive breeding program, which has in recent times focused on releasing higher numbers of juveniles into the wild.
"It's pretty exciting. It's definitely in the strongest spot (the species has been in) for a very long time," orange-bellied parrot program manager Paul Black told AAP.
Returning birds include 23 females and 17 males, surpassing the previous mark of 35 in the 2014-15 season.
Thirty captive birds raised at a government facility outside Hobart have been released to join them so far this spring, with more juveniles to be added to the flock early next year.
"There's been a lot of effort put into spring releases," Mr Black said, adding in February this year the flock numbered more than 110 with the addition of 49 juveniles.
He said parts of the bird's winter migration to mainland feeding grounds remained a mystery but all recent arrivals were in good condition.
Releasing a high number of juveniles was designed, in part, to give the birds safety in numbers, Mr Black said.
"You're going to be less likely to be predated by a raptor for example if you're in a larger group," he said.
"There's also the efficiency of migrating in a larger flock, so a single bird migrating on its own, backwards and forwards, is really going to struggle."
Orange-bellied parrots are one of three migrating parrot species in the world.
Scientists are looking at the possibility of establishing a second breeding population at a different location in Tasmania.
