Drones properly equipped to scare the heck out of pest birds may prove to be an effective and economical way to protect winegrapes from European starlings in the final days before harvest.
In a trial on three commercial vineyards, drones blaring out the sounds of a bird in distress, and carrying taxidermy that looks to the bird’s eye like a dead starling, proved almost as effective as the costly alternative of protecting the vines with nets.
“Our results suggest the system may have similar efficacy as netting,” said Zihao Wang, a doctoral student at the University of Sydney in Australia. “Netting is effective, but it is expensive both in terms of the cost of the netting and the cost of labor.”
Wang has spent five years studying pest bird psychology and developing, modifying and testing a drone-based system for keeping birds away from winegrapes and other vulnerable crops.
He discussed his latest results during the Virtual Sustainable Ag Expo and International Sustainable Winegrowing Summit, organized by the Central Coast Vineyard Team.
Wang said his complete system — with drones, cameras to know when the starlings have entered the vineyard and computerized controls to direct the drones — remains a few years from going commercial, but it looks as though it works.
“It may be two or three years down the road, but if you want to use the drones to deter the birds now, any decent-sized drone you can buy off the shelf right now can work in the short term,” Wang said. “It is probably more effective as a complement to your current management strategy, so you can use it to enhance the protection during the final week before the harvest.”
Wang built his system from the ground up, beginning with an understanding of how pest birds detect they are in danger and how they know it’s time to flee.
“How do birds recognize their natural predators?” he asked. “There are decades of research showing that birds recognize risk by observing other birds and listening to their calls. We installed a distress call through a loudspeaker on the drone that signals anti-predatory behavior.”
The prototype drones also carry taxidermy that looks like a dead starling or other target pest bird.
Wang said his current model — featuring a drone with propellers at all four corners, a small but loud speaker to broadcast the sounds of a frightened starling, and carrying what looks to be a dead bird — represented an advance on earlier versions that looked like a hawk, which invited attacks by hawks and eagles defending their territory.
“The drone has a unique shape, unlike any other natural flying animals,” he said. “Most of the (earlier) drones got attacked because the local predator is trying to protect its territory. Most of the drones that got attacked were fixed-wing t’s, which means they look like a bird. Since we decided to use the rotors as our prototype, and after we switched to the current configuration, we haven’t encountered any bird attacks.”
Once the drone was designed, the next step was to develop a system for knowing when the starlings or other pest birds were in the vineyard and directing the drone in pursuit.
“The system has a bird-detection system that can tell when the birds are coming,” Wang said. “For bird detection, we use four cameras set up at the corners of the vineyard and a camera on the drone to track the flight once the birds start to move away.”
The system was tested in the field, and Wang said it demonstrated it could scare off large flock birds such as white cockatoos and ravens, or smaller birds such as starlings, and that the birds did not return to the vineyard the rest of the day.
“It wasn’t the movement that deterred the birds,” he said. “It was the distress call and the bird taxidermy that did the job.”
He said his studies showed the drone can work effectively in a circle of vineyard more than a half-mile in diameter, scare off the pest birds from a distance of 50 yards or more, and keep them from returning the rest of the day.
Wang tried his system in three commercial vineyards, in a study comparing the relative effectiveness of reflective devices, netting, and the drone-based system.
“The visual scaring from the reflective devices was the least effective in all three vineyards,” he said.
The netting was most effective in two of the blocks, and the drones, which are potentially far more economical, in the third.
There are other tools for managing pest birds, including mobile loudspeakers, predator-shaped kites or other visual deterrents.
“These methods are cheap, but they suffer from habituation,” Wang said. “They may be effective when they are first installed, but usually within just one week the birds start to learn they don’t actually pose any danger, and they keep feeding on the grapes.”
Wang developed his system in Australia, where the government estimates birds damage 15% of the 360,000-acre winegrape crop, at an annual cost of $127 million.
But the need in California and throughout the nation is apparent: University studies concluded the European starling was causing more than $800 million in damage to crops in the U.S. by 2004, and that today all bird species combined may be causing nearly $5 billion in damage.