This is the kind of solar energy that doesn't incinerate birds. There's also the other kind. Photographer: Chip Chipman/Bloomberg
This is the kind of solar energy that doesn't incinerate birds. There's also the other kind. Photographer: Chip Chipman/Bloomberg

Workers at the power plant call them "streamers," like something you might toss during a parade or a New Year's Eve celebration.

But it's not about fun and games at a huge new solar-energy facility in California's Mojave Desert. When observers see something falling from the sky trailing smoke and flames, it isn't a fragment of space debris burning up in the atmosphere; it's probably a bird.

The Ivanpah Solar Electric Generating System, which opened in February, seems like the ideal green project. An array of 300,000 mirrors covering 3,500 acres focus the sun's rays on three 460-foot towers. The towers contain a liquid that, when heated, powers steam turbines. Those turbines in turn produce enough electricity for about 140,000 homes, without greenhouse gases or other emissions.

What no one seems to have counted on was how the facility, developed by BrightSource Energy Inc., would affect the environment. We now know the answer: It attracts birds and kills them.

After several studies, the conclusion for why birds are drawn to the searing beams of the solar field goes like this: Insects are attracted to the bright light of the reflecting mirrors, much as moths are lured to a porch light. Small birds -- insect eaters such as finches, swallows and warblers -- go after the bugs. In turn, predators such as hawks and falcons pursue the smaller birds.

But once the birds enter the focal field of the mirrors, called the "solar flux," injury or death can occur in a few seconds. The reflected light from the mirrors is 800 to 1,000 degrees Fahrenheit. Either the birds are incinerated in flight; their feathers are singed, causing them to fall to their deaths; or they are too injured to fly and are killed on the ground by predators, according to a report by the National Fish and Wildlife Forensics Laboratory. (Hats off to the Press-Enterprise in Riverside, California, which got the report through a Freedom of Information Act request.)

Parts of the report make for grisly reading. Here's an example:

Ivanpah employees and OLE (Office of Law Enforcement) staff noticed that close to the periphery of the tower and within the reflected solar field, streams of smoke rise when an object crosses the solar flux fields aimed at the tower. Ivanpah employees used the term "streamers" to characterize this occurrence.

When OLE staff visited the Ivanpah Solar plant, we observed many streamer events. It is claimed these events represent the combustion of loose debris, or insects. Although some of the events are likely that, there were instances in which the amount of smoke produced by the ignition could only be explained by a larger flammable biomass such as a bird. Indeed OLE staff observed birds entering the solar flux and igniting, consequently becoming a streamer.

The observers said they saw one streamer every two minutes.

The report goes on to document the carnage at other California power stations that rely on solar panels, rather than mirrors and heating towers, to collect energy from the sun. Birds at these facilities tended to fly into the panels, much as millions of birds do every year, whether into glass skyscrapers in cities or picture windows in suburban houses. But only at Ivanpah do birds ignite in flight.

Representatives of NRG Energy Inc., which operates Ivanpah, have challenged the report with an array of answers that seem like they come from a collection of greatest hits for corporate defenses: The plant is new; let's see what happens over time; the conclusions are premature.

What isn't in dispute is that other green-energy facilities have proven lethal for birds, too. Last year the U.S. Justice Department ordered Duke Energy Corp. to pay $1 million in fines and restitution for killing untold numbers of birds at wind-generation farms. Wind farms may seem innocuous, but they work more or less like giant blenders for birds, as well as bats. Among the most vulnerable are eagles and other raptors, which tend to fly head down scouring the ground for prey.

In all cases, the potential remedies seem inadequate to the task of minimizing bird deaths: not operating during peak migratory periods, using sonic devices to scare birds away, clearing larger areas around the facilities to remove habitats for birds and their prey.

In any event, this should remind us that generating power -- whether from fossil fuels, nuclear reactors or dammed rivers -- has a cost. The only question is which bad option we choose.

To contact the author of this article: James Greiff at jgreiff@bloomberg.net.

To contact the editor responsible for this article: Christopher Flavelle at cflavelle@bloomberg.net.