Small Birds of Great Deception: Cunning Vocal Mimicry

Scientists from the ANU have recently discovered the cunning strategies of a tiny native bird, which mimics the alarm calls of other birds to deceive its predators. The bird in question was the brown thornbill, which could mimic the calls of fairy wrens, honeyeaters, robins, rosellas and even currawongs.

The study suggested that distracting predators with alarm call mimicry may allow thornbill nestlings to scramble away from their main predators, currawongs. When ANU researchers played back currawong calls to brown thornbills at the National Botanical Gardens, the thornbills responded with a chorus of alarm calls. Dr Branislav Igic, who led the study, said in a press release: “It’s not superbly accurate mimicry, but it’s enough to fool the predator.”

The researchers then staged fake thornbill nests and played recordings of thornbills imitating the alarm calls of honeyeaters. “The predator firstly pauses, looks around, and then sometimes even flies away,” said Professor Robert Magrath, coauthor of the study, in a video interview in June.
He was fascinated by the results. “You have a tiny bird, maybe seven grams, which is deceiving a monstrous predator maybe 40 times its size.”

The little thornbill’s great powers of deception were actually unveiled by accident, recounts Professor Magrath. “When I was taking a group of undergraduate students on a totally unrelated project… I kept hearing sounds of birds that I couldn’t see. Eventually, I realised that it was the brown thornbill mimicking the calls of a variety of other species.”

Researchers from the ANU School of Biology published the study, titled “Crying wolf to a predator: deceptive vocal mimicry by a bird protecting young”, in the The Proceedings of the Royal Society in May.