Interpreting long‐distance movements of non‐migratory golden eagles: Prospecting and nomadism?

Type: journal article

Article abstract: Movements by animals can serve different functions and occur over a varietyof spatial and temporal scales. Routine movement types, such as residency(localized movements) and migration, have been well studied. However, non-routine movement types, such as dispersal, prospecting, and nomadism, areless well understood. Documenting these rarely detected events requires track-ing large numbers of individuals across all age classes. We studied >500 goldeneagles (Aquila chrysaetos) tracked by telemetry over a 10-year period in west-ern North America, of which 160 engaged in nonroutine, long-distance(>300 km) movements. We identified spatial and temporal correlates of thosemovements at both small and large scales, and we quantified movementtiming and direction. We further tested which age and sex classes of eagleswere more likely to engage in these movements. Our analysis of 88,093 dailytracks suggested that distances traveled by eagles were responsive to theupdraft potential of the spatial and temporal landscape they encountered.Tracks covered longer distances at locations and times of higher updraft poten-tial, and older birds traveled farther than younger birds. By contrast, afterdecomposing daily tracks into 563 nonroutine, long-distance movementsmeasured at a multiday scale, only the duration of travel was responsive toenvironmental conditions encountered by eagles. Multiday trips that werelonger were those initiated in open and warm landscapes and those that endedin mountainous regions. Finally, long-distance movements were morefrequently made in seasons other than winter, in north–south directions, andby young birds. We documented clear correlates of nonroutine, long-distancemovements by golden eagles at small, local scales but found little evidence ofsuch correlates at larger, regional scales. Most long-distance movements we documented fit patterns associated with traditional definitions of prospectingand nomadism but not migration. Our study is the first to describe these move-ment types by golden eagles, and as such provides a foundation for subsequentstudy into the movement ecology of other species.

Authors: Poessel, Sharon, A.; Woodbridge, Brian; Smith, Brian, W.; Murphy, Robert; Bedrosian, Bryan, E.; Bell, Douglas; Bittner, David; Bloom, Peter; Crandall, Ross, H.; Domenech, Robert; Fisher, Robert N.; Haggarty, Patricia, K.; Slater, Steven, J.; Tracey, Jeff; Watson, James, W.; Katzner, Todd;

Journal title: EcoSphere

Year: 2022

Volume: 13

Number: 6

Keywords: golden eagle;

Species: Golden Eagle; Golden eagle


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File owner: San Diego Management and Monitoring Program