The test of what works up above may come Down Under
ADELAIDE, Australia––Little corellas, the smallest of the cockatoo family, are again under the gun as purported avian pests in South Australia. Their cousins, long-billed corellas, are under attack in West Australia.
Another cousin, the allegedly invasive sulphur-crested cockatoo, native to New Guinea, has long been an unwelcome guest in Victoria state. Cocktoos are often shot, poisoned, or gassed by farmers who accuse them of stripping crops.
But drones may be coming to the rescue.
Noise alone is not the answer
Drones carrying noise-making devices are already used to a limited extent to try to drive corellas and cockatoos from problematic locations.
This technique, however, is often rejected by critics as “just moving the problem around.” Certainly it amounts to moving unwelcome noise around, noise being among the most frequent complaints issued against corellas and cockatoos.
Drone-delivered noisemakers may not be the ultimate answer to corella and cockatoo concentrations in problematic places.
Nonetheless, deployment of drones as bird-herders shows considerable potential for further development, according to University of Sydney aerospace engineer Zihao Wang in a newly published paper entitled “Psychological warfare in vineyard: Using drones and bird psychology to control bird damage to wine grapes,” published by the journal Crop Protection.
Mayor appeals for corella cull
The Wang paper appeared more-or-less simultaneously with an appeal from Keith Parkes, mayor of Alexandrina, a coastal city southeast of Adelaide, for funding from the South Australian government to gas corella flocks across the state.
“We believe a cull is required, and a substantial one, and it has to be statewide,” Parkes told Daniel Keane of the Australian Broadcasting Corporation on March 28, 2019.
“The damage they do to infrastructure is enormous,” Parkes said. “They rip up tennis courts and bowling greens. They make a hell of a mess, so it’s a big problem. We’ve tried shooting them. We’re currently using drones and other noisemaking devices to move them on,” Parkes said, but called them ineffective.
Little corellas “displacing cockatoos”
“The little corella has historically been confined to the northeast corner of South Australia but spread with the development of agriculture and irrigation, which provided new water and food sources,” reported Guardian correspondent Royce Kurmelovs in April 2018.
Adelaide University associate professor David Paton told Kurmelovs that the little corella arrived in the Adelaide region circa 1970.
“It took a while to happen,” Paton said, “but it’s at the stage now where in some places little corellas are displacing cockatoos from nesting hollows. The flocks are quite mobile.”
Wrote Kurmelovs, “Residents of north Adelaide say the birds have been turning up in increasing numbers every year for about six months at a time. Wherever they gather, signs of occupation can be found. Trees are stripped of their leaves, plastic equipment gets chewed up, and bird droppings, feathers and the occasional body of a fallen comrade litter the ground.”
A variety of noise-making techniques have been also used to roust little corellas from north Adelaide, including using drones to deliver the noise-makers to the vicinity of corella roosts, but as at Alexandrina, that approach has won mixed reviews, at best.
“The city of Bunbury recently announced a corella cull to remove 400 birds from the population each year for the next five years at a cost of $50,000,” Kurmelovs mentioned.
But Paton was skeptical, recalling that, as Kurmelovs summarized, “In the 1990s permission was given to cull the birds near Quorn,” about 200 miles north of Adelaide, “ but that experiment proved that when some of the flock was killed, others would come in from elsewhere to replace them.”
In West Australia state, long-billed corellas are the problematic species.
“The long-billed corella was introduced to West Australia as an aviary bird, but escapees flocked together to become a pest, crowding out local native species through competition for food sources,” Gian De Poloni of the Australian Broadcasting Corporation reported in January 2018.
Like Alexandrina mayor Keith Parkes, Geraldton mayor Shane Van Styn argued for wholesale culling, claiming long-billed corellas were doing $400,000 a year in damage to infrastructure.
Permits to kill 2,000
“We’re going to kill a few of these pesky little birds, and hopefully that sends a clear message to them to rack off,” Van Styn told De Poloni. “They will be netted after being lured to the ground using wheat or any other nice snacks that they might like to consume, at which point they’ll be rounded up and gassed.”
Wrote De Poloni, “The Department of Biodiversity, Conservation and Attractions issued permits to cull 2,000 corellas across the state last year. But West Australia Local Government Association president Lynne Craigie said that was not nearly enough.
Department of Biodiversity, Conservation and Attractions assistant director of conservation Fran Stanley cautioned that wholesale culls could kill species of corella other than those targeted.
Some corellas are protected
“It is difficult to tell the species apart. They all look relatively similar,” Stanley told De Poloni. “The ones we get in the Perth metropolitan area, for example are not native to this area, but still they are protected as fauna under the Wildlife Conservation Act.,” Stanley said.
Much as little and longbilled corellas, and sulpur-crested cockatoos, are despised by some people as pests and crop-raiders, they also fulfill a variety of essential ecological roles, including in distributing the seeds of many native plants.
University of New England professor emeritus of animal behavior Gisela Kaplan told Daniel; Keane of the Australian Broadcasting Corporation that the anti-corella views expressed by Parkes and Van Styn are “entirely inappropriate, cruel and ignorant. These large flocks [of little corellas] do not represent an overabundance of the species,” Kaplan said.
“One bird of prey will clear corellas in two to five minutes”
“The sum total of all the inland corellas have flocked together in a desperate, last-ditch attempt to stay alive. Taking the last remaining flocks of corellas and poisoning or shooting or gassing them is an absolutely reckless idea,” Kaplan continued.
“One single bird of prey, particularly a peregrine falcon, flying over an area with a flock of 10,000 corellas, will clear those corellas within two minutes to five minutes,” Kaplan insisted.
“This problem can be solved in a very short period of time,” Kaplan finished, “with very natural means, and be permanently successful.”
Birds of prey can be problematic, too
Kaplan recommended efforts to attract, and keep, birds of prey in locations where corellas and cockatoos are unwanted. But that approach also has drawbacks, particularly for farmers, who tend to regard birds of prey as threats to livestock.
In addition, setting out meat to feed birds of prey, as Kaplan suggested, could create odor and insect problems comparable to the effects of corella and cockatoo concentrations, and could attract dogs, cats, and rodents.
But the idea behind Kaplan’s recommendations might just work, the Wang study suggests, by outfitting drones to appear to corellas and cockatoos like their most feared predators.
Tested in vineyards
Summarized Brandon Keim for the March 27, 2019 edition of Anthropocene Magazine, “Ravens and cockatoos with a taste for grapes [are] no small matter: some Australian vineyards have reported crop losses of up to 83%, and current methods of crop protection leave much to be desired. Bird-excluding nets are cumbersome. Chemical repellents have unintended environmental consequences. Loud noises and scarecrows can work for a little while, but target animals soon become habituated to them,” while killing birds tends to just open habitat to more.
Hiring falconers to scare birds away from crops is effective but costly.
“Enter Zihao Wang and colleagues’ drones,” Keim wrote. “Drawing upon research into the responses of birds to unfamiliar predators, the researchers outfitted an off-the-shelf hexacopter [drone] with the taxadermied body of a dead crow, plus a loudspeaker that broadcast the distress calls of several bird species.
“The researchers figured that any bird confronted by that airborne grotesquerie would think the crow had been seized by some unknown beast.
Worked with four species, including cockatoos
“Indeed they did. Flocks chased by the drone, which was operated at a distance by the researchers, quickly fled,” Keim recounted, “and stayed away the rest of the day.
“More research on other species and over longer time frames is necessary,” Keim finished. “The trial runs involved only cockatoos, ravens, starlings, and silvereyes, and they might eventually learn that the drone is actually harmless — but the results are promising.”
Previous peer-reviewed literature investigating the use of drones to protect crops and otherwise control bird behavior has mostly been dismissive.
Skepticism from USDA Wildlife Services
For example, Michael L. Avery of the USDA National Wildlife Research Center and Scott J. Werner of USDA Wildlife Services, the federal government extermination agency, wrote in a 14-page 2017 review of “Frightening Devices” used for bird control that while flying devices have been tested for more than 40 years, “Constraints include that it requires a skilled operator, only relatively small areas can be covered, inclement weather inhibits operation, and it is labor-intensive.”
Avery and Werner acknowledged, however, that “Automated drone technology incorporating GPS-guided, programmed flight paths offers promise for new, improved effective hazing options in the near future.”
A Chicago company, Bird-X Inc., is already advertising what it calls “The first drone of its class made specifically for bird control,” which sounds much like the device Zhang Wang tested.
“Bird-X drones combine the visual and physical presence of a flying ‘predator,’” the Bird-X web site says, “with naturally-recorded predator cries and distress calls.”