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The beaches of Port Willunga, a coastal suburb 45 kilometres south of Adelaide, South Australia’s largest city, feel like an unlikely testing ground for animal-spotting drones. The holiday brochure-blue sea and cliffs with carved-out caves where fishermen used to store their boats give it the feel of a place that hasn’t changed much over the last couple of centuries.

But then Jarrod Hodgson arrived with his army of plastic birds. In May 2016, Hodgson, an ecologist from the University of Adelaide, brought thousands of life-sized plastic terns to the beaches in Port Willunga in order to answer a simple question. Ecologists are already using drones to keep tabs on animal populations, tracking whales in the Pacific and counting orangutans in Nepal, but no one is really sure if drone-based counts are more accurate than doing it the old-fashioned way, with binoculars and a hand-held counter.


To find out, Hodgson had to transform a stretch of beach into a drone testing ground. He arranged thousands of his fake birds into ten smaller colonies, each with between 460 and 1020 fake birds and tasked a small group of professional birdwatchers with counting the number of individuals in each colony. To avoid scaring away the plastic birds, small teams of birdwatchers positioned themselves 37.5 metres further up the beach – about as close as a human can get to a real greater crested tern colony without spooking the birds. From there, the birdwatchers used tripod-mounted spotting scopes and binoculars to count the birds.

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Above the birdwatchers' heads, an off-the-shelf quadcopter was already snapping photos of the fake colonies from distances of between 30 and 120 metres above ground, using a digital camera with the time-lapse function activated. Hodgson then asked people with only one previous experience of bird watching to manually count the number of terns they could spot in each drone snap. Although the amateur ornithologists did use counting software that helped them mark off each bird as they counted it, none of this counting was done automatically. He then compared the amateurs’ final tallies with the figures totted up by the birdwatchers.

“Our results show that is more accurate (and there is less error) to count surface breeding, colonial birds that can be seen from above using drone-captured imagery than from the ground,” Hodgson says. The drone-derived counts were, on average, between 43 and 96 per cent more accurate than the totals reached by the ground-based birdwatchers. In the wild, these figures might be even higher since real birds tend to move about a bit more than their plastic counterparts, making counting them by hand even more tricky. Hodgson published his findings in a paper published in the journal Methods in Ecology and Evolution.

This is a real-life Crested Tern colony – the species of seabird that was replicated in the experiment Jarrod Hodgson


“Our results have important implications for a range of species,” says Hodgson. “We consider they are especially relevant to aggregating birds, including seabirds like albatrosses, surface nesting penguins and frigatebirds, as well as colonial nesting waterbirds like pelicans. Other types of animals that are easily seen from above, including hauled-out seals and dugongs, are also highly suited to drone monitoring. Even when animals themselves can’t be seen, their nests or tracks can provide reliable indicators of their presence," he says.

Hodgson and his team also trialled a computer-vision system to help automate some of the bird-counting. Although the system wasn’t more accurate than humans looking at the same drone-captured images, Hodgson says that semi-automated counting systems could be useful for counting colonies containing many thousands of individuals.

But before ecologists start deploying swarms of tracking drones, they need to do more research into the impact that drones have on animals and their environments. A study published in the journal Cell in 2015 found that drones fly-bys raised the heart rate of black bears in Minnesota and eagles have been known to attack drones in the wild. “The results of such research will help to refine and improve drone monitoring protocols so that drones have minimal to non-existent impact on wildlife,” Hodgson says.