How much space does a powerful owl need to live the good life in Melbourne's suburbs? Researchers trapping and tagging up to 10 of Australia's largest owl species are about to find out.
The notoriously shy bird of prey with its startled "what are you looking at?" eyes is traditionally a forest species, though they are known to live around the green wedges and parks of Melbourne, Sydney and Brisbane. However, little is known about their nighttime travel habits in urban areas, making conservation work a challenge.
Listed as threatened in Victoria, the powerful owl is a fearsome predator, targeting ringtail and brushtail possums, flying foxes and even cats.
Deakin University environmental science honours student Nick Bradsworth said while there was no shortage of food for the owls in urban areas, the question of how much space they needed to live and breed well in suburbia remained unanswered.
In an effort to better understand the requirements of the urban powerful owls, Mr Bradsworth will trap and attach GPS trackers to the tail feathers of the birds, which can grow up to 65 centimetres tall and weigh around 1.6 kilograms.
There have been very few radio tracking studies of powerful owls because the birds are so difficult to catch.
"They are extremely cryptic birds," Mr Bradsworth said. "And being nocturnal, they can see extremely well in the darkness, so we can only set up traps on dark nights."
Trapping the large birds and attaching 30-gram GPS transmitters as part of a year-long research project should give the researchers the data they need to gain an understanding of the travel patterns of powerful owls - both those living in pairs and as "singles" in Melbourne's eastern suburbs. So far, six birds have been caught and tagged.
Mr Bradsworth's supervisor John White said it was thought that the urban population didn't travel as widely as their forest-dwelling cousins, due to the generous concentration of food (namely possums) in Melbourne's suburbs.
The GPS transmitter will also lead researchers to the birds' roosting sites. Being reliably messy eaters, inspecting the debris beneath the tree will give researchers an insight into the urban owl diet.
"We will be able to collect regurgitated pellets to look at their diet," Mr Bradsworth said. "The feathers fur, bones and exoskeletons from beetles is really interesting because we can see what they have been eating and if the urban diet is less diverse than the forest diet."
A wildlife ecologist, associate Professor White said because the owl was an apex predator in the suburbs, understanding their requirements was key to maintaining the balance in the finely tuned ecosystem, particularly keeping the possum population in check.
"Where you have good predator populations, you usually have a more diverse prey population," Associate Professor White said.
Deakin University wildlife ecologist Raylene Cooke estimated there were no more than 20 powerful owls living in the eastern suburbs of Melbourne. However, she said there were limited old trees with suitable nesting hollows, which could keep a lid on the urban population's breeding rate and upset the natural order. If this was established, researchers would look at introducing nesting boxes, she said.