First Satellite Telemetry Study of Movement Behavior of Juvenile Golden Eagles from Mexico

ABSTRACT The southern limit of the Golden Eagle's (Aquila chrysaetos) breeding range in North America is Mexico, where the eagle is the national symbol yet designated as a threatened, high priority species for conservation action. Movement information needed for conserving Mexico's Golden Eagles is sparse; knowledge of dispersal from natal areas is essential to understand the eagle's ecology and help provide for its management. Using satellite telemetry data, we analyzed movements of three males and one female from central Mexico during their first year of life; we documented (1) timing and distance of initial dispersal movements, (2) total distance traveled and maximum distance from natal site by month of age following fledging, and (3) size of areas (based on 95% adaptive local convex hulls) across which eagles ranged following initial dispersal. Individual eagles dispersed from their natal areas between mid-September and mid-November, at 6–8 mo of age. Monthly total distance traveled by males reached approximately 350–1350 km at 8–11 mo; the female's peak monthly travel was 3000 km, at age 7 mo. Monthly proximity to natal sites by individuals at ages 8–12 mo was relatively constant, averaging 17.9 km (SD = 5.7) to 129.1 km (SD = 11.3). After dispersal, the monthly ranging areas overall increased during the first year of life for all eagles, especially the female, due mainly to multiple long-distance excursions. Our data suggest that movement behavior of juvenile Golden Eagles from Mexico is mostly similar to that of conspecifics from nonmigratory populations elsewhere. Our study may help serve as a foundation for future work to better understand movement dynamics and resource selection by Mexico's Golden Eagles.

Can a Model of Avian Electrocution from Southern California be Useful in Guiding Power Pole Retrofitting for Golden Eagles Elsewhere?

A previously published model of avian electrocution risk, “the 2014 model,” was developed by comparing power poles that electrocuted birds (electrocution poles; including 21 golden eagle Aquila chrysaetos electrocutions) to poles not known to have electrocuted birds (comparison poles). The 2014 model produces pole-specific risk index scores between 0 and 1. The scores rank relative risk so electric utilities can maximize conservation benefits per dollar spent by focusing retrofitting on poles with greatest risk. Although the 2014 model was created from a study population of birds and poles in southern California, the 2014 model has potential to be used in managing a target population of raptors including golden eagles throughout the western United States. Use beyond southern California is only appropriate if the study population is similar enough to the target population for the 2014 model to predict risk effectively. To evaluate similarity, we examined five sources of evidence. Two were the relative consistency in electrical safety codes for power poles and body sizes of golden eagles in the study and target populations. Three more were consistency in structure-specific factors associated with 1) golden eagle electrocutions in other studies, 2) other avian electrocutions, and 3) previously unreported golden eagle electrocutions. We found that although the study population in the 2014 model included relatively few golden eagles, data were sufficient to create a model that can be applied to a target population throughout the western United States. The model can also be useful in helping determine equivalencies between pole types if utilities seek to compare benefits of retrofitting small numbers of high-risk poles to large numbers of low-risk poles.

Coyote (Canis latrans) predation of colonial rodents facilitated by Golden Eagles (Aquila chrysaetos)

Interactions between Coyote (Canis latrans) and Golden Eagle (Aquila chrysaetos) are complex and likely not yet fully documented or understood. I observed a Coyote prey on a Black-tailed Prairie Dog (Cynomys ludovicianus) at the edge of a large colony in Grasslands National Park, Saskatchewan. The prairie dogs were vigilant toward three Golden Eagles circling above, and the Coyote apparently used this to its advantage. As such, the eagles appeared to facilitate the ability of the Coyote to rush in virtually undetected and prey on a prairie dog that was distracted by the avian predators. This observation is of scientific interest because it is another example of the varied interactions between Coyotes and Golden Eagles, which is competitive and includes kleptoparasitism.

Non-territorial GPS-tagged golden eagles Aquila chrysaetos at two Scottish wind farms: Avoidance influenced by preferred habitat distribution, wind speed and blade motion status

Wind farms can have two broad potential adverse effects on birds via antagonistic processes: displacement from the vicinity of turbines (avoidance), or death through collision with rotating turbine blades. These effects may not be mutually exclusive. Using detailed data from 99 turbines at two wind farms in central Scotland and thousands of GPS-telemetry data from dispersing golden eagles, we tested three hypotheses. Before-and-after-operation analyses supported the hypothesis of avoidance: displacement was reduced at turbine locations in more preferred habitat and with more preferred habitat nearby. After-operation analyses (i.e. from the period when turbines were operational) showed that at higher wind speeds and in highly preferred habitat eagles were less wary of turbines with motionless blades: rejecting our second hypothesis. Our third hypothesis was supported, since at higher wind speeds eagles flew closer to operational turbines; especially–once more–turbines in more preferred habitat. After operation, eagles effectively abandoned inner turbine locations, and flight line records close to rotor blades were rare. While our study indicated that whole-wind farm functional habitat loss through avoidance was the substantial adverse impact, we make recommendations on future wind farm design to minimise collision risk further. These largely entail developers avoiding outer turbine locations which are in and surrounded by swathes of preferred habitat. Our study illustrates the insights which detailed case studies of large raptors at wind farms can bring and emphasises that the balance between avoidance and collision can have several influences.

Golden Eagle Abundance in Alaska: Migration Counts and Movement Data Generate a Conservative Population Estimate

ABSTRACT Estimating species density and abundance is challenging but important for establishing conservation and management strategies. Significant progress has been made toward estimating Golden Eagle (Aquila chrysaetos) abundance in the conterminous United States of America (USA) but much less is known about eagle abundance in Alaska. Here, we paired migration count and GPS-tracking data collected near Gunsight Mountain, Alaska, in a Bayesian framework to estimate the number of Golden Eagles in south-central Alaska. We estimated 1204 (95% credible interval: 866, 1526) potentially breeding (≥4 yr old) Golden Eagles annually moved through the Gunsight Mountain migration corridor and summered over an area of 150,325 km2 in south-central Alaska, equating to a density of 0.80 potentially breeding eagles/100 km2. By extrapolating across the species' nesting range in Alaska (1,180,489 km2) and incorporating published productivity and age-specific survival rates for eagles <4 yr old into our hierarchical model, we estimated 12,717 (95% credible interval: 9043, 16,349) Golden Eagles of all ages occur in Alaska, annually. We propose this as a conservative statewide population estimate because we used methods that likely underestimated population size. Even so, our estimate is three to five times larger than previous estimates and likely represents about one quarter of the USA's population.

Hunting for the Mythic Female Shaman Eagle Featuring the Golden Eagle (Aquila chrysaetos)

<p>This essay explores different intonations of the episode of the Female Shaman Eagle that is found in European versions of the Bear’s Son tale. It will be shown that a retelling of this episode can be detected in other myths and legends. It has left traces in the myth of Prometheus as summarized in Hesiod, as well as more explicitly in the legends surrounding the Caucasian hero Amirani. Further to the east the episode surfaces in tales recorded among the Tuvan people while evidence for the entrenchment of the episode along with its mythical ramifications in imagery can be identified in Iran. In the pages that follow we discover that the eastern reach of variants of the Bear’s Son tale takes us into Turkey, the Caucasus, south into Iran and even further to the east into the westernmost steppes of Mongolia. In all these geographic locations it is the figure of the Female Shaman Eagle that is highlighted and acquires mythic proportions, not just in narrative form but also as a highly esteemed bird of prey, celebrated in dance and expressed in striking visual imagery. In these materials the eagle in question is regularly identified as a Golden Eagle (Aquila chrysaetos). In addition, these are zones in which there have been strong traditions of raising and training Golden Eagles as hunting companions</p>