Drones have become an important tool in war, but these robotic flyers could have myriad uses off the battlefield, including as bird-watchers. Researchers may use drones to monitor wild birds without disturbing them and their natural habitat, researchers say.
For instance, drones could help investigators study birds nesting on cliffs and other places that are beyond human reach, scientists added.
Commercial drones, or unmanned aerial vehicles (UAVs), are becoming more and more affordable. Many videos on the Internet taken using drones reveal that researchers are increasingly using these robotic flyers to approach and study wildlife. [Photos from Above: 8 Cool Camera-Carrying Drones]
"More or less everyone can have access to small drones, at least in Europe," said study co-author David Grémillet, an ecologist at France's National Center for Scientific Research in Montpellier. "Sometimes you can buy them in a supermarket."
However, it remains unclear what impacts drones have on the animals they monitor. "Both researchers and members of the public are keen to approach birds with drones," Grémillet told Live Science. "But we're worried about the impact drones might have on birds. We've seen videos on the Internet where people clearly got too close to birds."
In the first study of the potential effects of these drones on birds, Grémillet and his colleagues flew small, camera-equipped, four-rotor "quadricopter" drones on more than 200 flights. The drones were each about 2.2 lbs. (1 kilogram) in weight and 13.7 inches (35 centimeters) wide, and came in three colors — white, black and blue. They were relatively quiet, making only about 60 decibels of noise at a distance of 6 feet (2 meters), which is about as loud as a normal conversation.
After getting permits from the French government to fly the drones to study wildlife, the researchers analyzed the effects of drones on mallards that live in a zoo in France but are free to fly in and out of the premises. The scientists also studied wild flamingos and common greenshanks living in a lagoon in France.
"Flamingos and greenshanks are really sensitive to disturbances," Grémillet said. "They are shy and very easily scared off.".
The drones were launched at a minimum distance of 165 feet (50 m) from the zoo birds and 330 feet (100 m) from the wild birds. The drones approached the birds at speeds of up to nearly 18 mph (29 km/h). While a trained and licensed pilot steered the drones, scientists watched the birds with binoculars and used laser rangefinders to determine how far the drones were from the birds.
Surprisingly, the researchers found that on 80 percent of the flights, the drones could approach within 13 feet (4 m) of these birds without visibly affecting the animals' behavior. Drone speed and color did not affect the birds' behavior. [9 Totally Cool Uses for Drones]
"It was a really big surprise to us that we could approach birds so closely without visibly disturbing them," Grémillet said. "It was really interesting that the approach speed didn't have an impact."
Drones are "so foreign to birds that there's no reaction in most cases," Grémillet said. The findings are similar to a recent study that examined the effects of robots on penguins.
The scientists did find that birds disliked being approached vertically, and often flew away.
"The birds preferred to be approached by something they could see rather than something approaching them vertically, which makes sense," Grémillet said. "If something was coming toward you that you could identify as nonthreatening, that's fine, but if something's hovering over your head, you could get scared."
These results suggest that when drones are carefully flown, they could be useful tools for research on birds.
"There's great potential here," Grémillet said. "Colleagues study seabirds in Norway known as kittiwakes, which breed on huge cliffs that are very inaccessible. If you have a drone, you could fly safely along the cliffs to count their numbers and observe their behaviors. Also, imagine studying birds breeding in huge wetlands. Right now, you have to put on waders and slowly wade into these scattered habitats, and you'd disturb the birds as you approach them. Drones could fly over and study them without disturbing them."
The researchers did caution that while the drones usually did not have any visible effects on the birds, this does not necessarily mean the flying robots did not create stress for the birds.
"Birds have really good poker faces — their heart rates could be going through the roof, as well as levels of the stress hormone cortisol, and we wouldn't see it," Grémillet said. "Prior studies found that when penguins are exposed to tourists or helicopter flights, they don't react behaviorally, but their heart rates would go high. We would want to do more work studying whether drones have these kinds of effects, as well."
Future research can analyze the effects of drones on different kinds of birds. Some birds, such as gulls, or crows and their relatives, "might attack drones, and they would get injured, so that's bad," Grémillet said. "We'd also want to follow birds at different times of their lives. Birds might be less sensitive at the beginning of breeding seasons since they are full of hormones called prolactins that lower stress levels, but toward the end of breeding seasons, they might react more to drones."
The scientists would also like "to test different types of drones, such as fixed-wing drones, which have shapes more like birds and could remind birds more of predators such as hawks or eagles," Grémillet said. "We'd also want to test larger drones, which can make quite a lot of noise."
Drone laws differ between France and the United States. In 2013, the U.S. Federal Aviation Administration (FAA) laid out a preliminary plan for overseeing commercial drone use, but comprehensive guidelines for small drones are not expected until later this year. In the meantime, the FAA has announced that television and movie producers can now apply to use drones to capture high-flying aerial footage.
The scientists detailed their findings online Feb. 3 in the journal Biology Letters.