The 1920s were still relatively early in the days of widespread access to electric power. The high-voltage lines carrying electricity from hydroelectric dams in the Sierra Nevada to consumers in Los Angeles were considered a magnificent feat of technological innovation, yet this massive and expensive system quickly came under threat from an unexpected source: bird poop.

A new paper in the journal Environmental Humanities by Etienne Benson, an assistant professor in the Department of History and Sociology of Science in the School of Arts & Sciences, explores this tale and what it says about the relationship between humans, technology, and the environment.

“I’ve been interested for a long time in human-animal relationships and how they’re transformed by technological developments,” Benson says.

Always keeping an eye out for relevant stories, Benson came across an article written in 1928 by engineer and amateur ornithologist Harold Michener, who described how birds threatened to bring down a whole power grid in the early 20th century.

“At first I thought he was exaggerating, that he just wanted to tell a cool story,” Benson says. “But as I dug into it, I found corroborative evidence that it was actually a serious problem.”

According to Benson, after the power company Southern California Edison upgraded their lines to carry 220,000 volts—among the highest voltage lines in the world at the time—the grid began experiencing frequent short circuits, interrupting service and threatening to damage transformers and other equipment. The company investigated the problem for months but couldn’t figure out what could be causing it—that is, until someone looked up at a transmission tower and saw a raptor perched on top.

“They had a brain flash that it’s actually the birds’ excrement that causes it. They did lab tests and found it was possible,” Benson says.

Their hypothesis was that hawks and eagles were attracted to the transmission towers as high lookout points from which to hunt. The jets of excrement they released when launching from the towers could carry electric current from the wire to the steel tower, causing a short circuit.

In response, the company installed barriers, spikes and excrement-catching pans on the towers—at considerable cost. The problem soon dissipated although it never vanished completely. In addition, as the power grid became more sophisticated, it was segmented and automatic relays were installed so that power could be more easily restored.

Benson notes that all of these interventions were invisible to consumers, who could simply flip a switch and light a room without considering the hard work and environmental impact behind the generation of power.

“We may think we’re separate from nature, but actually everything we do is deeply embedded in it,” Benson says. “The modern industrial landscape, which seems so hard and durable, requires constant maintenance for it to continue seeming hard and durable.”