Wildlife carers released 36 birds from aviaries on the Bellarine Peninsula, on the northern shore of Western Port Bay, and near Werribee on Wednesday.

Five years ago there were less than 50 orange bellied parrots, and only four females, left in the wild, but a large-scale captive-breeding and release program has managed to boost numbers significantly in just a few years.

While it's hard to say exactly how many parrots there are now, more than 180 birds have migrated from their breeding grounds in Tasmania in 2021.

"Considering where we were, it's really astounding what we have now," DELWP Project Coordinator Rachel Pritchard told AAP.

The captive-bred birds took about an hour to fly out of their aviaries on Wednesday morning, and they did not seem to be in a hurry, stopping to eat bird food before flying away.

The aviaries will be left open in case the parrots need to return for food or shelter.

It's hoped they will attract other parrots that are currently migrating to Victoria from south-west Tasmania, and together the birds will establish flocks in high-quality habitat.

The parrots spend summer breeding in Tasmania where they nest in the hollows of eucalypt trees near button grass plains.

They migrate to spend winter in South Australia and Victoria, where they usually stay within 3km of the coast.

They are one of only three migratory parrot species in the world.

The species has become critically endangered due to habitat loss, predation by cats and foxes, and inbreeding due to their small population.

Orange-bellied parrots are fitted with leg bands, and the released birds are also fitted with radio trackers.

Australian Associated Press