Human activities are killing wildlife at unprecedented rates, with causes ranging from environmental pollution to the built environment. For some bird species, night-time collisions with power lines are driving substantial population declines. But now scientists have come up with a clever way to make the cables easier for birds to spot, without being unsightly to humans.

Industry and U.S. Fish & Wildlife Service guidelines recommend that utility companies mark their power lines with plastic attachments to increase visibility, but birds are still dying. Biologists reported that 300 Sandhill cranes perished in one month in 2009 from collisions with marked lines at the Rowe Sanctuary in Nebraska, where the cranes stop over during their annual spring migration. “We need forward-thinking methods to protect not only large birds that are inherently at greater risk from power lines but also millions of smaller migratory birds,” says Anne Lacy of the International Crane Foundation.

Half of all avian species can see ultraviolet light. So James Dwyer, a wildlife biologist at utility consulting firm EDM International in Fort Collins, Colo., had the idea of using near-visible UV light to illuminate power lines. EDM's engineering team and the Dawson Public Power District developed such light systems and installed them on a tower supporting a power line at Rowe Sanctuary. Over a 38-night period, crane collisions decreased by 98 percent when the lights were on, the researchers reported in a study published online in May in Ornithological Applications.

Richard Loughery, director of environmental activities at the Edison Electric Institute, who was not involved in the project, says the new UV system adds an important tool for use in hotspots where endangered bird species nest and feed.

The researchers did not observe any negative impacts on other species: insects did not swarm toward the lights, nor did bats or nighthawks do so in pursuit of a meal. And Dwyer says birds are unlikely to confuse such near-ground UV illumination with natural cues such as starlight.

“I don't want utilities to build lines wherever they want because there's a new tool,” says biologist Robert Harms of the U.S. Fish & Wildlife Service, who was not involved in the work. But for existing lines, he says, the UV system could be “absolutely amazing.”