Seasonal, Diel, and Spatial Dispersion Patterns of Golden Eagle Autumn Migration in Southwestern Montana

Omland, Kristian Shawn; Hoffman, Stephen W.

doi:10.2307/1369577

Cited by 7 publications

(8 citation statements)

References 3 publications

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“…6c). Although temporal patterns in movement have been relatively well studied (Omland & Hoffman 1996, Soutullo et al 2005, Cadah ıa et al 2007, Poessel et al 2016, the population-level spatial variation we measured in movement is not commonly incorporated into those studies. In fact, accounting for spatial variation in movement was central to accurate interpretation of our data and may be an important component to future work in this field.…”

Section: External Environmentmentioning

confidence: 99%

Relevance of individual and environmental drivers of movement of Golden Eagles

Sur

Duerr²,

Bell³

et al. 2019

Ibis

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An animal's movement is expected to be governed by an interplay between goals determined by its internal state and energetic costs associated with navigating through the external environment. Understanding this ecological process is challenging when an animal moves in two dimensions and even more difficult for birds that move in a third dimension. To understand the dynamic interaction between the internal state of an animal and the variable external environment, we evaluated hypotheses explaining association of different covariates of movement and the trade‐offs birds face as they make behavioural decisions in a fluctuating landscape. We used ~870 000 GPS telemetry data points collected from 68 Golden Eagles Aquila chrysaetos to test demographic, diel, topographic and meteorological hypotheses to determine (1) the probability that these birds would be in motion and (2), once in motion, their flight speed. A complex and sometimes interacting set of potential internal and external factors determined movement behaviour. There was good evidence that reproductive state, manifested as age, sex and seasonal effects, had a significant influence on the probability of being in motion and, to a lesser extent, on speed of motion. Likewise, movement responses to the external environment were often unexpectedly strong. These responses, to northness of slope, strength of orographic updraft and intensity of solar radiation, were regionally and temporally variable. In contrast to previous work showing the role of a single environmental factor in determining movement decisions, our analyses support the hypothesis that multiple factors simultaneously interact to influence animal movement. In particular they highlighted how movement is influenced by the interaction between the individual's internal reproductive state and the external environment, and that, of the environmental factors, topographic influences are often more relevant than meteorological influences in determining patterns of flight behaviour. Further disentangling of how these internal and externals states jointly affect movement will provide additional insights into the energetic costs of movement and benefits associated with achieving process‐driven goals.

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Section: External Environmentmentioning

confidence: 99%

Relevance of individual and environmental drivers of movement of Golden Eagles

Sur

Duerr²,

Bell³

et al. 2019

Ibis

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“…1). The Hart Range is also part of a known Golden Eagle migration corridor that follows the Rocky Mountains from Alaska/Yukon to wintering grounds in the mid-and southwestern United States (Omland and Hoffman 1996, Yates et al 2001, Sherrington 2003, McIntyre et al 2008, Bittner 2010. Dokie 1 is the first operational facility within the Hart Range, and the site topography and weather are representative of those found throughout the Hart Range and the eastern Rocky Mountains (Yates et al 2001, Sherrington 2003.…”

Section: Study Area Dokie 1 (55°46′28″ N 122°16′48″ W) Is Located Inmentioning

confidence: 99%

Flight Paths of Migrating Golden Eagles and the Risk Associated with Wind Energy Development in the Rocky Mountains

Johnston¹,

Bradley²,

Pomeroy³

et al. 2013

ACE

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ABSTRACT. In recent years, the eastern foothills of the Rocky Mountains in northeastern British Columbia have received interest as a site of industrial wind energy development but, simultaneously, have been the subject of concern about wind development coinciding with a known migratory corridor of Golden Eagles (Aquila chrysaetos). We tracked and quantified eagle flights that crossed or followed ridgelines slated for one such wind development. We found that hourly passage rates during fall migration peaked at midday and increased by 17% with each 1 km/h increase in wind speed and by 11% with each 1°C increase in temperature. The propensity to cross the ridge tops where turbines would be situated differed between age classes, with juvenile eagles almost twice as likely to traverse the ridge-top area as adults or subadults. During fall migration, Golden Eagles were more likely to cross ridges at turbine heights (risk zone, < 150 m above ground) under headwinds or tailwinds, but this likelihood decreased with increasing temperature. Conversely, during spring migration, eagles were more likely to move within the ridge-top area under eastern crosswinds. Identifying Golden Eagle flight routes and altitudes with respect to major weather systems and local topography in the Rockies may help identify scenarios in which the potential for collisions is greatest at this and other installations.RÉSUMÉ. Récemment, les contreforts des Rocheuses dans le nord-est de la Colombie-Britannique ont attiré l'attention comme site potentiel d'un développement éolien industriel, tout en faisant simultanément l'objet de préoccupations puisque ce projet coïnciderait avec un corridor de migration connu d'Aigles royaux (Aquila chrysaetos). Nous avons suivi et quantifié les vols d'aigles qui ont traversé ou longé les lignes de crêtes visées par un projet éolien de ce genre. Nous avons constaté que le taux de passage horaire durant la migration automnale atteignait un maximum à midi et augmentait de 17 % pour chaque km/h d'augmentation de la vitesse du vent, et de 11 % pour chaque °C d'augmentation de la température. La propension à traverser les sommets des crêtes où seraient installées les éoliennes différait selon les classes d'âge, les jeunes aigles de l'année ayant deux fois plus de chance de le faire que les adultes ou les jeunes plus âgés. Durant la migration automnale, les aigles traversaient davantage les crêtes à hauteur d'éoliennes (zone de risque, < 150 m au-dessus du niveau du sol) sous un vent de face ou arrière, mais cette tendance diminuait avec l'augmentation de la température. En revanche, durant la migration printanière, les aigles étaient plus susceptibles de survoler la région des sommets sous un vent latéral de l'est. La détermination des trajectoires et des altitudes de vol des Aigles royaux, selon les systèmes météorologiques prédominants et la topographie locale des Rocheuses, peut contribuer à identifier les scénarios dans lesquels les risques de collision sont les plus élevés, que ce soit pour ce projet éolien ou d'au...

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“…Although golden eagles are considered to be solitary migrants (Omland and Hoffman 1996), I observed clustered passage in both seasons; however, group size was larger in the spring and included a greater proportion of the total individuals observed (50% of all birds detected in the spring versus 25%o in the fall). In the fall, the greater occurrence of aggregated passage in the afternoon and at lower wind speeds may be associated with the greater prevalence of thermal availability in the afternoon, which can slow down migration speed and aggregate birds Bruderer 1997, Klaassen et al 2008).…”

Section: Local Migration Routes and Aggregated Passagementioning

confidence: 68%

“…These criteria result in a conservative estimate which excludes birds that were travelling along the same route but at distances greater than my cut-off. However, it should be noted that at any point in time, eagles could change their flight direction relative to the other birds in the group, and as such an individual migration route is considered independent from other birds (Omland and Hoffman 1996).…”

Section: Data Preparationmentioning

confidence: 99%

“…Although I did not identify associations between hourly passage and barometric pressure in the fall, other studies on soaring raptors have. For example, some studies found daily raptor passage to be associated with the passage of cold fronts (Hall et al 1992, Allen et al 1996, Omland and Hoffman 1996, or hourly passage to be explained by a drop in barometric pressure (Millsap andZook 1983, Thomas 2008). Others, however, found increased hourly passage to be associated with an increase in pressure (Allen et al 1996, Yates et al 2001).…”

Section: Migration Patternsmentioning

confidence: 99%

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The associations between weather and topography on golden eagle flight behaviour at a wind farm in the Canadian rockies.

Johnston¹

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Seasonal, Diel, and Spatial Dispersion Patterns of Golden Eagle Autumn Migration in Southwestern Montana

Cited by 7 publications

References 3 publications

Relevance of individual and environmental drivers of movement of Golden Eagles

Relevance of individual and environmental drivers of movement of Golden Eagles

Flight Paths of Migrating Golden Eagles and the Risk Associated with Wind Energy Development in the Rocky Mountains

The associations between weather and topography on golden eagle flight behaviour at a wind farm in the Canadian rockies.

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