In 2014, a wildfire ripped through central Chile, destroying 2500 homes and killing at least 13 people. A year later, a blaze in Idaho burned more than 4000 hectares, an area nearly 12 times the size of New York City’s Central Park. Both conflagrations had one thing in common: Experts believe they were started by birds.
Our feathered friends love to perch on power lines, which can be a great place to rest and launch an attack. But if a bird touches the wrong wires together, or somehow forms an electrical pathway to the ground, it can get fried. Falling to the floor like winged Molotov cocktails, birds can spark an inferno if they hit an especially dry, tindered patch of earth.
More than three dozen fires started this way in the United States from 2014 to 2018, according to the most comprehensive analysis yet of such blazes. “The ecological and economic losses are substantial,” says Antoni Margalida, a conservation biologist at the Pyrenean Institute of Ecology who has studied the impacts of wildfires caused by birds and other fauna in Spain but who was not involved with the work.
Humans are responsible for the vast majority of wildfires in the United States. Lightning and even heat from the Sun can also spark blazes. But flaming birds have gotten less attention.
To better document this fowl play, Taylor Barnes, a biologist at EDM International, an engineering consultancy firm in Colorado, collected data on wildfires across the United States. He and his colleagues used Google Alerts to monitor fires started by birds between 2014 and 2018, using keyword pairs: “fire” and “eagle,” for example. They filtered out any findings unrelated to power lines, such as those referring to vehicles. “The Pontiac Firebird came up a lot,” Barnes says.
The scientists then discounted any speculative reports, only keeping those with evidence of a bird as the cause. These could include a photograph of a burned bird carcass at the fire’s ignition site, or a statement made by an expert, such as a firefighter, detailing the presumed cause of the fire. Finally, they checked to see whether any particular environment was especially susceptible to these fires.
The researchers found 44 reports of avian-induced wildfiresthey report this month in the Wildlife Society Bulletin. Twelve (the densest cluster of northern fires) occurred in an ecological region that stretches from southern Oregon through California to Mexico, bounded by the Pacific Ocean and the Sierra Nevada mountains. This area, a diverse mix of valleys, hills, and mountains, has a warm Mediterranean-style climate unique to North America, with mild, wet winters fed by the ocean, followed by hot, dry summers. It is also prone to severe droughts. This combination creates large amounts of vegetation in the winter that quickly dries out to become potential fuel.
“That’s why we see a lot of fires going to the catastrophic level,” Barnes says. The region is also densely populated, which may make unwanted urban-wildlife interactions, such as electrocuted large raptors (hawks, eagles, and owls) more likely. “The interaction between humans developing more in raptor habitat could certainly be a driver,” he says.
The wildfires reported in the study were generally small: Most of them burned about 1.2 hectares, a touch over two US football fields. Yet there is a clear potential for large-scale devastation, as the Idaho and Chile fires show.
Powerlines aren’t just a fire hazard; they’re also a threat to birds. A recent study in Iran found that of the 235 birds electrocuted there in 2018, 15% were species of conservation concern such as the steppe eagle (Aquila nipalensis) and the Egyptian vulture (Neophron percnopterus). Birds of prey—particularly those with large wings such as buzzards and eagles—are especially vulnerable to electrocution at power poles, says Graham Martin, an ornithologist at the University of Birmingham. “When landing or taking off from the perch, they are likely to touch two wires simultaneously.”
Bird electrocutions are “an emerging problem” around the world, Margalida says. To minimize wildfire impacts, he says, electric utilities in regions characterized by wet winters and hot, dry summers should modify power infrastructure.
Electric utility companies can insulate wires and install spikes to discourage perching; they could also build structures that allow for safer perching on transformers, Barnes says.
Such engineering can be expensive, he admits. But, he says, “Compared to the potential financial costs of litigation, and loss of human life, loss of infrastructure, they are minor costs.”