Frequency disruption shifts birds from aircraft strike zones

Friday, May 27, 2016

Academics have devised a harmonious solution to an aviation hazard blamed for more than 250 deaths since 1988.

Researchers from the University of Exeter have installed “sonic nets” at a US airfield to ward off birds capable of bringing down aircraft.

The study, reported in the journal Ecological Applications, marks the latest in a string of largely ineffective techniques trialled to prevent bird strikes. They have included shooting, poisoning and relocating birds and blasting them with sound and light.

Lead researcher John Swaddle said “startle and alarm” methods had not worked because birds learned to live with them. “Loud noises are not a real threat,” he told The Australian.

“People have generally tried to come up with new ways of scaring birds off with different sounds and visual stimuli (such as) lights, flashing tape (and) models of predators. Again, the birds habituate to these new stimuli.”

The Exeter team concocted a subtler approach: interrupting the frequencies of bird communication.

“We focused on stopping the birds hearing each other and predators,” Professor Swaddle said. “Areas where they can’t listen for risks and threats, which are ever present in nature, are permanently more dangerous to occupy. The birds leave as long as there is somewhere else to go.”

The trial took place in three areas of an airfield in Virginia. The researchers set up amplifiers that broadcast noise at the same pitch as birds’ warning calls and predators’ screeches.

They recorded bird abundance for a month before switching on the speakers, and another month afterwards. Bird numbers decreased by about 80 per cent in the “sonic net” areas. Species known for aircraft collisions, such as starlings, proved particularly sensitive.

The university said the birds showed no sign of becoming habituated to the noise, which was about as loud as a crowded restaurant. It said the approach was a benign and cheap solution to bird strike, which was estimated to cost the aviation industry $US937 million ($1.29 billion) a year in the US alone.

“Our idea works because (it) makes an area acoustically untenable,” Professor Swaddle said. “The crucial areas to protect are the ends of the runways where the majority of bird strike occurs. We contain the sound with highly directional speakers so we’re not increasing noise in the general vicinity.”

He said the approach could also be used to deter birds from crops and wind turbines and clear communities of flying fox colonies.

Last month the Australian Transport Safety Bureau issued a guide to help protect aircraft from wildlife. It says airport operators should vary their dispersal methods to avoid desensitising animals.

Over the decade to 2013, more than 14,500 wildlife strikes were reported to the ATSB, with high-capacity aircraft averaging 7.4 strikes for every 10,000 movements. General aviation recorded 1445 wildlife incidents.

Black kites, galahs, plovers and bats proved the biggest threats. Black kites were particularly dangerous because of their size, weighing more than half a kilogram each. Galahs are smaller but congregate in flocks, boosting the risk of multiple strikes.

Published in The Australian
written by John Ross

Higher Education reporter
Sydney