No one knows for sure how many birds are killed by the Altamont turbines -- a 2004 California Energy Commission report estimated the golden eagle toll to be between 75 and 116 a year, while total bird kills were put in the 1,766 to 4,721 range. The Audubon Society lawsuit targets four raptor species -- golden eagle, red-tailed hawk, American kestrel and burrowing owl -- which suffered 456 to 1,129 fatalities per year, the study estimated.
Subsequent data indicate that bird deaths have not decreased since the settlement was reached last January and that efforts to achieve a 50 percent reduction in three years are far behind, said Shawn Smallwood, an independent consultant in avian ecology who co-authored the 2004 California Energy Commission study and is one of the five county-appointed scientists.
There are tradeoffs to almost everything we do, but in this case the solution clearly favors upgrading older turbines to more modern models, which operate at a higher level with more slowly spinning blades.