New research from The Australian National University (ANU) has found genetic evidence that critically endangered swift parrots, which breed all over Tasmania and on predator-free islands, form a single nomadic population at high risk of extinction.
Nomadic swift parrots breed across Tasmania wherever their food is most abundant.
Dr Dejan Stojanovic from the ANU Fenner School of Environment and Society said DNA collected from nestling swift parrots showed those birds from predator-free Bruny Island and Maria Island were not genetically isolated from populations on mainland Tasmania.
He said the findings supported the need to manage the swift parrot population as a single unit, and that even local threats like deforestation and predatory sugar gliders may impact large proportions of the mobile parrot population.
"We already recognise the importance of predator-free islands as havens for swift parrots, but our findings demonstrate that protecting islands is only part of the solution to saving the parrots," he said.
"This new genetic evidence shows that islands don't support a genetically distinct subpopulation of swift parrots. Birds that nest on islands in one year may move to the Tasmanian mainland the next year, putting them at risk of being eaten by sugar gliders."
Dr Stojanovic said the genetic findings supported previous predictions of severe extinction risk to swift parrots from loss of habitat and sugar glider predation on mainland Tasmania.
"Protecting islands from deforestation is a good start for the swift parrot, but this alone will not save them from extinction. We need to better protect mature forests on mainland Tasmania to stop these birds from going extinct" he said.
The work is part of the Difficult Bird Research Group at ANU, which focusses on Australia's most endangered birds and is dedicated to understanding their ecology and conservation.
The research was published in Animal Conservation.