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Tiny bird ‘cries hawk’ to distract predators from nestlings

US Rep. Ilhan Omar (D-MN) (L) talks with Speaker of the House Nancy Pelosi (D-CA) during a rally with fellow Democrats before voting on H.R. 1, or the People Act, on the East Steps of the US Capitol on March 08, 2019 in Washington, DC. (AFP photo)
A brown thornbill

A new study has revealed that a tiny species of birds can distract nest predators by mimicking hawk alarm calls made by other species, warning the attackers that much bigger raptorial birds are around.

The six-gram thornbills have evolved a technique that enables them to mimic the goshawk alarm calls produced by other small neighboring species in order to scare away nest raiders such as currawongs, read the research conducted by scientists at the University of Cambridge and the Australian National University (ANU) and published on Tuesday in the journal Proceedings of the Royal Society B.

Pied currawongs, 40 times bigger than a thornbill, are sensitive to hawk alarm calls made by other species to help them avoid being hunted by coming goshawks. Therefore, the medium-sized black passerine bird take the false alarm made by the thornbills as a real call and leave the tiny birds alone.

“The enormous size difference between a tiny thornbill and a 0.5-kg goshawk might make it difficult for thornbills to mimic hawk vocalizations accurately, limiting them to mimicking the chorus of hawk alarm calls given by small local species instead," said Jessica McLachlan, a PhD student from Cambridge's Department of Zoology and the co-author of the study.

“As hawks are silent when hunting, the alarm calls of local species may be the only sound that warns of a hawk's presence,” she further noted.

When currawongs are distracted by the fake alarm-calls, thornbill nestlings will have enough time to escape. “Distracting a currawong attacking the nest could give older thornbill nestlings a chance to escape and hide in the surrounding vegetation,” said Dr. Branislav Igic from ANU and the director of the study.

“It's perhaps the thornbills best nest defense in this circumstance because physical attacks on the much larger currawong are hopeless,” Igic added.

Mimicking toxic or dangerous species to deter predators is relatively common among certain animals.


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