The highly endangered orange-bellied parrot has started returning to Tasmania's remote south-west to breed, and experts are hopeful the wild population could be significantly boosted this season.

There are only 30 to 50 parrots left in the wild, and 18 have already arrived at Melaleuca for the mating season.

Wildlife biologist Shannon Troy said two of the returned parrots were released in a trial earlier in the year.

"We didn't know if we'd get any back," she said.

The birds make the treacherous journey from Tasmania to south-west Victoria and South Australia during winter and return in late spring to breed.

Dr Troy said it was a risky journey.

"They're a budgie-sized bird and they have to cross Bass Strait," she said.

This male injured his leg over winter and may not be able to breed. ( Supplied: Mark Holdsworth )

Hopes high for summer breeding

Friends of the Orange-Bellied Parrot spokesman and ornithologist Mark Holdsworth said he was hopeful this summer could see the breeding capacity doubled.

"It's almost already surpassing our predictions so it's really exciting news," he said.

"We've still got a few more weeks to go for more birds to arrive."

So far, they have seen the best parrot numbers in years.

"It's still a very low number, of course," Mr Holdsworth said.

"I'm hopeful this season we will see a significant increase in the number of wild birds."

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In February, one-month-old birds were released into the wild — it was the first time juvenile parrots had been released late into the summer.

"They managed to go away for winter and they've come back to Melaleuca," he said.

"That's a really exciting development."

Little is known about where the birds go during winter.

Mr Holdsworth said only three or four birds were sighted this winter.

"Where the rest go is a mystery."

The thousands of kilometres of coastline make monitoring a challenge.

Dr Troy said work was underway to build up a flock interstate to act as a beacon for first-time migratory birds and help them choose appropriate habitat.

'Ranching' trial a success

To minimise the risk of the birds dying during their migratory paths to the mainland, 15 juvenile birds were held back in Tasmania this winter.

It's a strategy known as ranching and was trialled for the first time.

All 15 ranched birds survived and they will be released in stages.

Dr Troy said she was hopeful they'd have a high survival rate.

"I'm hoping the ranched birds will breed really well," she said.

Some of the orange-bellied parrots were ranched over winter. ( Supplied: Mark Holdsworth )

Mr Holdsworth said the past five years had been "depressing" for the parrots.

"We've seen this bird slowly go down the gurgler," he said.

"We'll see a doubling of the potential breeding capacity this summer.

"Of course we can't count our chickens until the end of the season because ultimate success is only measured by successful breeding."

The parrots nest in tree hollows, but at Melaleuca they've been given help with the construction of artificial nest boxes.

The boxes allow experts to monitor the eggs, and researchers from the Australian National University are conducting the first checks on them.

Injured male may not be able to breed

One of the population's older birds, known as Blue Orange C, injured its leg over winter.

Mr Holdsworth said the injury might prevent him from successfully breeding.

"To put it delicately, the males have to mount the female, and with a bung leg that might be a bit tricky to balance in the right place.

"It's possible he won't successfully mate with the female."

The eggs may end up infertile but could be replaced with fertile eggs for the female to foster.