Two air currents of planetary scale, the Pacific Ocean wind and Central Valley thermal, meet at northern California’s Altamont Pass, one hour east of San Francisco, to support both America’s largest wind farm and densest population of golden eagles. The wind farm supplies the burgeoning Bay Area with electric power while providing a diversity of air currents for hunting eagles to soar upon.
Wind moves at an average 15 mph through the pass, which stands at an altitude of 1,010 feet, while the wrinkled Coastal Range that the pass splits offers a complex pattern of canyons and hills populated by California ground squirrels, chief food of the nesting eagles. These conditions support roughly 200 pairs of nesting eagles and a further influx of winter migrants, with approximately 5,500 wind turbines arrayed in deadly opposition.
Hans Peters, Professor Emeritus of Biology at neighboring Chabot College, offers startling insight on the singularity of this habitat. The density of golden eagle nests within the 50,000-acre tract between Mts. Diablo and Hamilton, landmark summits bordering the Altamont Wind Farm, approaches 1 nest per half-mile at some points, whereas a typical separation distance for the species is at least 15 miles. This eagle congregation nests in the spotty oak woodland that cloaks the scheme of steep slopes, preferring north-facing ground.
The birds launch into the Altamont Airshed, their winds fixed upon prey, locked into air currents, as the blades of wind turbines lock in a high-speed spin. The resultant meeting of 100-m.p.h. wings and 200-m.p.h. blades sacrifices about 70 eagles per year.
Efforts to refit the wind farm for greater efficiency, thereby reducing the number of turbines, lag due to budgetary constraints, protracting a conflict that ensued in the 1970s with the coming of the wind farm. Turbine blades whirl above blowing folds of grassland commanding an ancient ecojuncture transformed into a point of struggle between eagle and energy freedom.