A variety of triggers can ignite wildfires on dry land: high winds whipping power lines together, stray cigarette butts, even sparks from train wheels. And sometimes electrocuted birds.
In 2017, a hawk with a snake lit a 40-acre fire in Montana. The accidental arsonist was found crispy on the floor, the well-done dinner still clutched. The snake-hawk duo would have touched two power lines at once, creating a circuit that electrocuted both before falling and igniting the grass. That was one of at least 44 wildfires caused by electrocuted birds in the United States from 2014 to 2018, researchers reported this month in the Wildlife Society Bulletin. Anecdotes of fires caused by birds crop up every now and then, and researchers are still trying to understand how much of a wildfire risk really results from such fowl.
Such electrocutions typically occur in areas with few trees, where larger bird species may perch or nest on utility poles, said Taylor Barnes, a geospatial information systems specialist at EDM International, a utility consulting firm, and one of the authors of the paper. A bird can rest on one wire without any problem. But touching two wires at once or touching one wire and a piece of grounded equipment, such as a transformer, can cause problems.
“When electrocutions occur, it is not uncommon for the water in the animal cells to immediately turn to steam,” said James Dwyer, a wildlife biologist also at EDM International and a co-author of the paper. “It explodes the cells and it will blow off a limb.”
Sometimes the bird’s plumage ignites and it can suffer on the ground.
“It’s a really hard way to go if it doesn’t happen right away,” he said.
There’s no database of bird-caused fires, so the researchers scoured news reports for combinations of words such as “fire” and “eagle,” preserving them with photographic evidence of charred birds or comments from firefighters or utility companies.
Most of the fires the team found were small—less than five acres, or about 12 acres, the size of a few city blocks. But one caused by a bird of prey in 2015 burned 10,000 acres in Idaho. The incendiary birds included eagles, hawks and turkey vultures, but in many cases the type of bird was not reported.
Mapping these burns against ecoregions — areas defined by their similar ecosystems and environmental resources — found that the Mediterranean region of California, much of the western part of the state, had the highest number of bird fires, despite this was the smallest area.
The higher density of fires in the region, caused by bird electrocution, may be due to heavy spring rains, which encourage rapid vegetation growth. Then comes summer heat, which dries all that new growth, creating fuel for fires that is relatively easy to ignite, said Dr. dwyer. There may also be a greater density of electrical infrastructure, such as utility poles where birds can be electrocuted.
Overall, the density of wildfires caused by bird electrocution was minuscule compared to the total wildfire density in all regions. “We’re not talking about a lot of inflammation,” said Jon Keeley, a fire ecologist with the US Geological Survey in Sequoia National Park in California, who was not part of this study. The vast majority of wildfires are caused by humans, and this is another example of that, he said. “It’s something that’s caused by human infrastructure.”
Power lines pose a threat to birds around the world, including endangered birds of prey that winter in North Africa and migratory birds that migrate through China, said José Rafael Garrido López, a wildlife biologist for the Environment and Water Agency of Andalusia in Spain, who is also not involved. was in this study. It is estimated that in the United States alone, about 10 million birds can die each year from electrocution, and even more die from collisions with electrical infrastructure.
Occasionally, a rare bird-induced inferno also leads to human deaths. A 2014 fire in Valparaíso, Chile, burned thousands of homes and killed 15 people. A 10-month investigation yielded electrocuted birds.
To reduce the risk of wildfires from birds, utilities can cover wires on the posts with plastic insulators to prevent birds from frying themselves. It’s a simple solution, and some utility companies in the United States are working to reduce bird electrocution and fire risks, said Dr. dwyer. In some places, conservationists have also attempted to place nest boxes on utility poles to prevent birds from nesting near metal wires or other equipment.
“The costs of mitigation are much lower than the potential impacts of these fires,” whether it be loss of life, loss of wildlife habitat or damage to electrical infrastructure, Mr Barnes said.