0453 GMT February 29, 2020
On Friday, the juvenile birds were released into the Yellingbo Nature Conservation Reserve, located 45 km east of Melbourne which holds the only wild population of critically endangered helmeted honeyeaters, in an unusual attempt at genetic species rescue, theguardian.com wrote.
The researchers say that without interbreeding, fertility rates within the 230-strong wild population could drop so low that the species would not survive.
The hybrids are the product of judicious crossing of the yellow-tufted honeyeater with the helmeted honeyeater, a closely related sub-species, at Healesville Sanctuary, outside Melbourne.
The sub-species diverged about 50,000 years ago and interbred in the wild until the helmeted honeyeater population dropped so low that it became isolated from its nearest relatives.
It is one of 20 key species targeted under a $30 million program by Zoos Victoria to prevent species extinction.
A study of 33 years of genetic and breeding data from the wild helmeted honeyeater population, published in the journal Current Biology this month, said the predicted lifetime reproductive success for a bird that was the product of several generations of inbreeding was up to 90 percent lower than that of the least inbred individuals.
Failure to address inbreeding, the study said, would “slow or prevent population recovery, even under intensive management interventions”.
The manager of conservation and research at Healesville, Kim Miller, said the hybrid breeding program mimicked historic breeding patterns in the wild.
“We know that as recently as 30 years ago there was regular genetic transfer between the two subspecies,” Miller said.
“That has been essentially disrupted by habitat fragmentation. Our objective is really to replicate what would happen under normal circumstances for these two subspecies.”
Healesville bred two generations of the hybrid birds to ensure they were “robust, healthy, and capable of breeding themselves”.
Miller said the program was intended to restore fertility rates for wild honeyeaters and would be monitored to ensure the integrity of the unique sub-species was not compromised.
“We have a really good plan in place for how much genetic diversity we are looking to introduce,” she said. “That’s enough to restore the level of genetic transfer between the two species back to its historic levels.”
The birds appear identical to helmeted honeyeaters. The president of Friends of the Helmeted Honeyeater, Alan Clayton, said he could not tell the hybrids apart.
“The little critter doesn’t stay still long enough in the wild for you to get a good look anyway,” he said.
The organization was founded in 1989 and has been the main source of in-field monitoring of the birds, as well as conducting habitat restoration. Volunteers have planted more than 3 million trees and shrubs, focusing on the honeyeater’s preferred habitat of Eucalyptus ovata and Eucalyptus camphora.
“If we do nothing but continue our efforts on this, there is an 87 percent risk of it being extinct from the consequence of inbreeding in 50 years anyway,” Clayton said.