Fig 1.
The Altamont Pass windfarm as viewed from its southern boundary in April 1995.
The dense configurations of small turbines in this photo are currently being replaced by fewer, larger, and more widely spaced machines.
Fig 2.
The Diablo Range golden eagle study region of west-central California showing the location of the Altamont Pass Wind Resource Area (hatched area) relative to: 1) the core study area where we monitored territory occupancy and reproduction of golden eagles, and 2) the broader Diablo Range study area where we used aircraft to regularly monitor movements and survival of radio-tagged eagles during 1994–2000, and where Wiens et al. [22] conducted occupancy surveys in 2014 and 2015.
Fig 3.
Golden eagle life cycle.
Fig 4.
High quality nesting habitat for golden eagles in the Diablo Range, California.
Fig 5.
Monthly variation in the proportion of individual golden eagles detected in the windfarm at least once per month in aerial surveys of 101 juveniles (radio-tagged as fledglings), 155 subadults, 51 floaters, and 47 breeders in the Diablo Range study area, 1994–2000.
The increase in percentage of juvenile occurrence in the windfarm resulted as eagles radio-tagged as fledglings in May and June dispersed from their natal territories during September–November of each year.
Table 1.
Results of golden eagle nest surveys in the Diablo Range study area, 1996–2000.
Table 2.
Ages of breeding golden eagles at territories within 30 km of the Altamont windfarm.
The asterisk indicates that the calculation included two individuals of uncertain age and therefore gave the maximum possible representation of subadults for that year. Note that yearly variation in the number of aged eagles reflects differences in sampling effort rather than population.
Table 3.
Causes of death among 88 uncensored golden eagle fatalities during 1994–2000.
Juveniles include only those radio-tagged as fledglings. Undiagnosed fatalities included four unrecovered individuals (see Methods).
Table 4.
Probability of annual survival () for four stage-classes of golden eagles radio-marked in the vicinity of the Altamont Pass Wind Resource Area, California, 1994–2000.
We show survival estimates with and without turbine-related and known human-caused deaths included in the analysis. All undiagnosed deaths were treated as "natural" so as to obtain a maximum estimate of natural mortality (see text). No juveniles were killed by turbine blade-strikes.