Biologists believe overhead electrical power lines and car collisions make a two-mile (3.2-kilometer) stretch of highway through the Audubon National Wildlife Refuge one of the world's deadliest places for birds, on land or air.
Recently, biologist Darren Doderer located casualty No. 373, a mangled and bloodied double-crested cormorant that appeared to have hit one of the dozen or so unmarked overhead power lines.
"It's not fun to see these deaths," said Doderer, who estimated he's walked about 500 miles (800 kilometers) in the area searching for dead birds since April.
Bird-vehicle crashes have not been addressed but a $1 million federal study, funded in part by utilities, is evaluating three types of "diverters" designed to make the power lines visible to birds, or scare them off a crash course.
One of the devices is shaped like a corkscrew and wraps around about 2 feet of the power line. Another diverter resembles a perforated neon pie plate with a reflective center. The third is about the size of an envelope, with reflectors attached and flaps in the wind.
The diverters cost between $8 and $40, and last from a year to two decades. Burying the power lines is considered a fix that's too expensive.
The three-year project by the U.S. Fish and Wildlife Service and the Western Area Power Administration concludes next month and biologists say it appears the various diverters have cut the number of birds strikes.
"What we're hoping to show is that no matter what you put on the line, it will be better than nothing," said Misti Schriner, a Denver-based biologist with Western Area Power Administration, which owns the power lines.
Schriner said birds dying after hitting power lines, wind turbines and buildings are a problem worldwide. Lessons learned from the North Dakota study could be applied to other areas that have high incidents of avian mortality, she said.
Schriner said 429 avian carcasses were recovered in 2006 when no diverters were used. Last year, 344 dead birds were recovered after hundreds of the devices were latched to some of the power lines. So far this year, 375 carcasses have been found, said Doderer, a biologist hired to find bird carcasses along the causeway.
Power lines along the causeway are linked by 11 spans. The diverters are placed only on power lines in selected spans, and some wires are left bare to compare results.
"Hopefully, the birds are benefiting from this," Doderer said. "But I don't think it has made a substantial difference."
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