In 2015, a wildfire burned through 10,000 acres in Idaho, forcing 165 firefighters to combat the blaze. The cause? A bird nesting at the top of a power line structure.
Reports of bird electrocutions leading to wildfires have shown up anecdotally from time to time in the past. Now researchers are studying just how often this happens, reports the New York Times’ Carolyn Wilke.
“When electrocutions happen, it’s not unusual for the water in the animal cells to be instantly turned to steam,” James Dwyer, a wildlife biologist at EDM International, a consulting company for electric utilities, and a coauthor on a new paper, tells Wilke. “It explodes the cells, and it’ll blow off a limb.”
In a paper published in Wildlife Society Bulletin, researchers collected data for birds causing fires from being electrocuted throughout the contiguous United States from January 2014 through December 2018. There is no central database for this sort of thing, so they got creative. They set up Google Alerts for three keyword searches: bird (and) fire, eagle (and) fire, and hawk (and) fire, and filtered out unrelated results.
Next, they manually sorted through the results and discarded wildfires that were not confirmed to have been started by a bird, looking for photographic evidence of a burned carcass at the ignition site or a statement made by an expert. Lastly, they mapped the fires out against ecoregions to see whether any one area was more susceptible to bird-caused fires than others, per Science’s Richard Kemeny.
The team found a total of 44 wildland fires caused by bird electrocutions in the U.S. within those five years.
“The ecological and economic losses are substantial,” Antoni Margalida, a conservation biologist at the Pyrenean Institute of Ecology who has studied wildfires caused by birds in Spain, but was not involved in the new study, tells Science.
Power lines are an attractive resting area, and birds often nest on utility poles and towers. Usually, a wire is a safe place for the animals to relax because the electrical current traveling through it is too small to shock the bird.
But if a bird touches two wires of different voltages at the same time or touches a wire and a grounded portion—like a pole—this gives the current a path to the ground and the birds can get fried. This is especially dangerous for fast-flying larger birds, such as raptors, eagles, vultures and storks.
“A lot of times the jumper wires running from the main conductors down to those transformers are uninsulated. So they’re energized, and birds can make contact with those tightly spaced wires or other pieces of energized equipment,” lead author Taylor Barnes of EDM tells KJZZ’s Nicholas Gerbis.
Most of the fires the team documented were small, but they discovered that the dry Mediterranean climate of large portions of California—an area already prone to drought—had the highest density of bird-caused fires.
Still, compared to all wildfires, those ignited by electrocuted birds are relatively few, per the Times (there were about 60,000 wildfires across the U.S. in 2021). But companies are working on ways to reduce the risk to bird-caused fires anyway, including covering wires on poles with plastic insulators, per the newspaper. The number of birds killed by electrocution far outweighs the number of fires they cause as well, with somewhere between one to ten million birds killed by electrocution at power lines every year.
“The cost of mitigation is far less than the potential consequence of these fires,” Barnes tells the publication.