Rare birds returned to Dirk Hartog Island in WA after local extinction

With brownish feathers, distinctive fine white streaks, and a long cocked tail, the western grasswren (Amytornis textilis) is a charming but elusive native Australian songbird.

If you are lucky enough to spot one, you might find it darting between shrubs as it forages along the ground on Dirk Hartog Island in Western Australia – thanks to the first successful grasswren translocation effort last month.

It was  to re-establish the population after the introduction of sheep, goats, and feral cats caused the birds, and 12 other species, to become extinct on the island.

These efforts are a part of the Dirk Hartog Island National Park “Return to 1616” Ecological Restoration Project: a major conservation science project run by the Department of Biodiversity, Conservation and Attractions (DBCA) that aims to return the vegetation and habitats of the island, to its condition when first visited by the Dutch explorer Dirk Hartog in 1616.

A small songbird with a distinctive squeaky song, the western grasswren were once found from Shark Bay in WA to the Eyre Peninsula in South Australia. Now, they’re restricted to Shark Bay and the north-eastern Eyre-Peninsula only, as their range contracted after European colonisation due to habitat loss.

Why 85 birds?

The translocation was informed by the PhD project of researcher Aline Gibson Vega, in a collaboration between DBCA, Bush Heritage Australia and the University of Western Australia.

Gibson Vega determined, from their genetics and behaviour, that birds could be safely relocated from the nearby Bush Heritage Hamelin Reserve and Francois Peron National Park in WA.

About 85 birds were moved in October, with the hope that it would maximise genetic diversity.

“It was so rewarding to see my research being used to inform the translocation planning and execution,” says Gibson Vega. “If my modelling is accurate, the 85 individuals will create a self-sustaining population and we may not need to do any further ‘top-ups’ of individuals in future years – though long-term monitoring will confirm this.”

A team of 12, split up into four teams of three, spent two weeks trying to capture family groups of western grasswrens in specifically designed mist-nets. Suitable grasswrens were then transported to the island via helicopter to be released that same day.

“It was very exciting to see the first grasswrens taking off to their new island home (now free of introduced predators) after all the research, planning, and hard work leading up to the moment,” says Dr Michelle Hall, Bush Heritage ecologist.

What’s next?

Some of the grasswrens were fitted with transmitters to monitor their movements and survival after being released onto the island.

“We’ve been busy tracking them, following them around as they settle in to their new home. And some of them seem to quite like where we’ve put them, others have moved a little way. But so far they seem to be settling quite well,” says Dr Saul Cowen, Biodiversity and Conservation Science, DBCA.

Audio recording units will also be used to monitor the birds over the long term by recording their calls; it’s estimated the Dirk Hartog Island will support up to 8,000 pairs of western grasswrens.

“The western grasswren represents being over the halfway mark in terms of the number of species that are planned to be reintroduced to Dirk Hartog, so that in itself is a significant milestone,” Cowen adds.

Other locally extinct species include the Shark Bay bandicoot, chuditch, mulgara, dibbler, greater stick-nest rat, desert mouse, Shark Bay mouse, heath mouse, woylie, and boodie. These species are being returned to the island alongside the banded and rufous hare-wallabies – two species that were also highly likely to have once lived on the island.