Bid to save birds from predatory Tasmania devils on Maria Island haven
A Tasmanian devil sanctuary established on Maria Island is taking a toll on the island's bird population.
Tasmania's Environment Department is being forced to protect nests to safeguard vulnerable birds on the east coast island.
The ambitious program to safeguard the iconic marsupial from a deadly facial tumour was started in 2012.
Twenty-eight devils were released on the island, which is cut off from the diseased devil population on mainland Tasmania.
The population has grown to more than 90, raising questions about the effect the apex predator is having on the island's other species.
The devils have been attacking ground-nesting birds and there is anecdotal evidence that no chicks have been successfully reared this breeding season.
"I'm not happy to see them here, I think it's most unfortunate," Maria Island ferry owner John Cole-Cook said.
"Why should we threaten the 120 species of birds that use this island as a sanctuary of the predators?"
The translocation of the devils to isolate them from the contagious facial cancer has been hailed a huge success, but the department is now assessing its next step.
Wildlife biologist Phil Wise is connected to the devil translocation program.
"With the proposal to put devils on the island, we did consider the risk to other species and some of the predictions we outlined in that proposal are starting to play out now," he said.
7.30 Tasmania has obtained pictures of Tasmanian devils attacking the Cape Barren Island Geese population.
Devils targetting native bird chicks
The geese were moved to Maria in the 1960s to safeguard them from predators, following a drop in their population.
"This year, we've had no Cape Barren geese chicks," Mr Cole-Cook said.
"The devils obviously are getting the eggs, as they would for the eggs of the other species, the penguins, the shearwaters, the hooded plovers."
Mr Wise said it was complex issue.
"We're in a difficult situation where Tasmanian devils are finding it difficult to survive in their natural range and Cape Barren geese are surviving well in their range, so it is a balancing act trying to protect the largest predator marsupial in the world," he said.
"With little penguins, we understand there is some impact in the Darlington area, we are certainly seeing feathers in their scat around that area,
"We're going to implement artificial nesting burrows closer to the water's edge which gives penguins the chance to get to the safety of the water before devils can get to them."
Ian Johnstone runs an up-market bushwalking business on Maria Island.
While he is happy the devil program is successful, he wants more monitoring done to ensure the long-term survival of other species.
"They describe Maria as Tasmania's Noah's Arc - lots of animals - it's one of the best places in Australia really, to see wildlife," he said.
"By introducing top-end carnivores like devils, it really puts pressure and unless you manage the balance of the right number of devils on the island, you're going to have problem.
"We've only seen one native hen chick alive this season, so that's a real concern."
Island visitors raise the alarm
Visitors to the island have also noticed unusual behaviour in the bird population.
Karin Ludwig is a former specialist on the giant macaws from New Zealand.
After camping at the Darlington settlement on the northern side of the island for a week, she noticed the bird species changing behaviour.
She would often hear the bird population alarm calling throughout the afternoon because Tasmanian devils were nearby.
"They are just alarm calling, it's a predator to them and the Tassie devils would eat their eggs and chicks," she said.
The island's little penguin population is also suffering.
"With little penguins, we understand there is some impact in the Darlington area," Mr Wise said.
"We are certainly seeing feathers in their [the devil's] scat around that area."
Mr Wise said the department was making moves to build protective nesting boxes to try and minimise the impact on the penguins.
"We're going to implement artificial nesting burrows closer to the water's edge which gives penguins the chance to get to the safety of the water before devils can get to them."
Devil experts suggest the island has almost reached its carrying capacity for devils.
"We can predict the final population size, or density of devils on the island from similar locations," academic Menna Jones said.
"Somewhere between 70 and 100 devils would be the carrying capacity for the island."
"There's only ever as many predators as there is prey to feed them, so they won't go wildly out of control."
With that number almost reached, Mr Wise said the focus would soon shift to translocating some of the healthy Tasmanian devils back to areas of mainland Tasmania.
