NRSI has had success using marine radar systems installed in vehicles, even though radar is usually designed to filter out birds and bats rather than track them, Stephenson says.
Field workers also use high-tech acoustic equipment to capture bat sounds at night.
But even the most state-of-the-art electronics can prove no match for the rough outdoors. On one occasion, field workers left the acoustic equipment out overnight, only to find the next morning that the wires had been eaten by a coyote.
Like other wind energy proponents, Stephenson says the industry has learned from the mistakes of the early days.
Today's turbines are located away from typical bird flight paths, thanks to services provided by firms such as NRSI. They are also several times taller and spin far more slowly than the death traps that were built in Altamont Pass.
NRSI says that for every bird that now dies at a wind turbine, about 3,500 are eaten by cats, 2,800 are smashed by cars and 150 collide fatally with cellphone towers.
"If you have windows on your house, and you drove here and you are on a cellphone, you've probably killed more birds than a wind turbine is responsible for in a year," Stephenson says.