By Ethan James in Hobart

Tiny tags attached to the legs of critically endangered orange-bellied parrots could reveal the “missing link” about their perilous journey across Bass Strait.

The migratory species was in dire trouble half a decade ago, when just 20 individuals were left in the wild.

This summer, scientists counted 188 parrots leaving their mating grounds of Melaleuca in southwest Tasmania for the south coast of mainland Australia.

The species is propped up by a captive breeding program which released 18 captive-bred adults in spring and 40 captive-bred juveniles in late summer.

There were a record 74 fledglings produced from 33 nest boxes at Melaleuca – the most recorded since monitoring began in 1993.

“(Overall, these are) low increases, but increases we’re happy to see,” orange-bellied parrot project manager Shannon Troy said.

About 80 birds returned to Tasmania in summer – the biggest cohort in about 15 years – but roughly 50 from the group that set out didn’t make it back.

“(We) need to figure out where is going wrong and why,” Dr Troy said.

“It could be lots of things, predators, habitat loss, experienced birds getting lost.”

Researchers have attached nanotags to 46 parrots that will transmit signals to 20 receiver towers dotted along Tasmania’s west coast and on Bass Strait islands.

“(This data) really is the missing link for their recovery,” Dr Troy said.

“We can keep doing good work at Melaleuca… but if we don’t know what is happening in the middle and why they’re not getting there, it is really difficult to continue growing the population without our intervention.”

Tasmania’s government has provided funding for the two-year tracking project.

Environment Minister Nick Duigan said the state government was committed to the protection, monitoring and management of the species.

There are fears a proposed wind farm at Robbins Island in northwest Tasmania, backed by the state government, could kill or injure migrating orange-bellied parrots and other birds.