A pilot golden eagle population study in the Altamont Pass Wind Resource Area, California

Abstract

Orloff and Flannery (1992) estimated that several hundred reports are annually killed by turbine collisions, wire strikes, and electrocutions at the Altamont Pass Wind Resource Area (WRA). The most common fatalities were those of red-tailed hawks (Buteo jamaicensis), American kestrels (Falco sparvatius), and golden eagles (Aquila chrysaetos), with lesser numbers of turkey vultures (Cathartes aura), common ravens (Corvus corax), bam owls (Tyto alba), and others. Among the species of raptors killed at Altamont Pass, the one whose local population is most likely to be impacted is the golden eagle. Besides its being less abundant than the others, the breeding and recruitment rates of golden eagles are naturally slow, increasing their susceptibility to decline as a result of mortality influences. The golden eagle is a species afforded special federal protection because of its inclusion within the Bald Eagle Protection Act as amended in 1963. There are no provisions within the Act which would allow the killing ``taking`` of golden eagles by WRA structures. This report details the results of field studies conducted during 19941. The primary purpose of the investigation is to lay the groundwork for determining whether or not turbine strikes and other hazards related to energy at Altamont Pass may be expected to affect golden eagles on a population basis. We also seek an understanding of the physical and biotic circumstances which attract golden eagles to the WRA within the context of the surrounding landscape and the conditions under which they are killed by wind turbines. Such knowledge may suggest turbine-related or habitat modifications that would result in a lower incidence of eagle mortality.