It turns out that harnessing solar energy means dealing with really high temperatures. Here's how a similar plant runs in California, according to E&E:
The 45-story "power towers" shine with sunlight reflected by 350,000 heliostat mirrors spread across an area four times the size of New York's Central Park. Receivers atop the towers heat to nearly 1,000 degrees Fahrenheit, boiling water to turn turbines that crank out 392 megawatts — power for more than 100,000 houses.
Rudy Evenson, Deputy Chief of Communications for Nevada Bureau of Land Management in Reno, says the birds are likely attracted to a glow caused by the highly-concentrated solar energy. Pair that glow with those high temperatures, and you get bird soup.
So far, an estimated 130 birds have been roasted during the plants testing periods, or turned into "streamers," or "trails of smoke and water vapor caused by the birds entering the field of concentrated energy."
Since the first test in January however, plant operators have made adjustments and a test done the following day had seemed to take care of the problem.
A subsequent test on January 15 reduced the number of mirrors aimed at the focal point above the tower, said Evenson, and that apparently ended the injuries to birds.