As preparations continued to bring a controversial solar project online in the Mojave Desert, November saw fewer reported injuries to birds on the site compared to the month before.
According to compliance documents filed with the California Energy Commission (CEC) and posted on the CEC's website Tuesday, 11 birds and one bat were found dead on the Ivanpah Solar Electric Generating System (ISEGS) site in November, down from 52 birds and six bats in October.
Of the 11 dead birds reported, two, a blackbird and a yellow-rumped warbler, were described as bearing "scorched or singed" feathers, an indication of overexposure to the plant's concentrated solar flux. Three other birds exhibited signs of having collided with heliostats or other equipment, and the remainder -- as well as the one pallid bat found dead on the site in November -- were recorded as having died of "unknown" causes.
Species making up the death toll included two yellow-rumped warblers, two greater roadrunners, a rock dove (a.k.a. common pigeon), an American pipit and a Savannah sparrow, as well as three birds that could not be completely identified.
ISEGS, being built by Bechtel for BrightSource Energy and its partners in the Ivanpah Valley near the Mojave National Preserve, consists of three power blocks with 459-foot towers surrounded by 170,000 mirrored heliostats, which will concentrate reflected sunlight at boilers atop the towers. When the plant finally goes online, slated for sometime early in 2014, it will generate a maximum of 377 megawatts of electrical power for California utilities.
It's unclear from the compliance report whether the plant was generating concentrated solar flux over a similar time period in November as in October, but as deaths from collisions with heliostats and other equipment also dropped in November. Assuming there were no irregularities in mortality reporting or surveys -- or, for that matter, greater solar flux consuming birds beyond biologists' ability to detect them -- that would account for the difference, the drop in numbers would seem to indicate that October's higher death toll is related to pulses of seasonal bird migration through the region of the Mojave Desert.
While a drop in overall numbers of injured birds is certainly welcome news on the face of it, if the project poses a special risk to migrating birds its environmental impact could well extend across a startlingly wide swath of North America.
Injuries to wildlife recorded at ISEGS were cited last week by the CEC as a reason to propose denying a permit to build BrightSource's Palen Solar Electric Generating System (PSEGS) in Riverside County. PSEGS, which brightSource hopes to build with its partner Abengoa Solar, would use technology similar to but on a significantly larger scale than Ivanpah's. The CEC is expected to make a final decision on that project in January.
According to the November compliance document, ISEGS' three units are between 98.5 and 99.8 percent complete, and contractor Bechtel is in the process of tearing down its construction infrastructure on the site.