Birds cry wolf to scare away predators
"It's not superbly accurate mimicry, but it's enough to fool the predator," said Dr Branislav Igic, who carried out the study during his PhD at the Australian National University.
"A physical attack on a currawong would be no good. They are 40 times the size of a thornbill and will eat adults as well as nestlings.
"I am amazed that such a tiny bird can mimic so many species, some much bigger than itself. It's very cunning," said Dr Igic, who has now taken up a position at the University of Akron, in Ohio, United States.
Although vocal mimicry is widespread amongst birds, its function is rarely understood. This study is the first to show that birds use vocal mimicry to scare predators.
The researchers stumbled across the thornbill's deceit during an experiment on birds' reaction to a stuffed owl.
"I was puzzled because I could hear the alarm calls of robins, honeyeaters and rosellas, but I couldn't see any," Professor Robert Magrath, the leader of the research group at the Research School of Biology.
"I soon realised that the brown thornbill was mimicking the other species, and and Branislav later discovered that they sometimes lie about the type of predator present when defending their nests," he said.