Document Type
Article
Publication Date
2012
College/Unit
Davis College of Agriculture, Natural Resources and Design
Department/Program/Center
Division of Forestry and Natural Resources
Abstract
To maximize fitness, flying animals should maximize flight speed while minimizing energetic expenditure. Soaring speeds of large-bodied birds are determined by flight routes and tradeoffs between minimizing time and energetic costs. Large raptors migrating in eastern North America predominantly glide between thermals that provide lift or soar along slopes or ridgelines using orographic lift (slope soaring). It is usually assumed that slope soaring is faster than thermal gliding because forward progress is constant compared to interrupted progress when birds pause to regain altitude in thermals. We tested this slope-soaring hypothesis using high-frequency GPS-GSM telemetry devices to track golden eagles during northbound migration. In contrast to expectations, flight speed was slower when slope soaring and eagles also were diverted from their migratory path, incurring possible energetic costs and reducing speed of progress towards a migratory endpoint. When gliding between thermals, eagles stayed on track and fast gliding speeds compensated for lack of progress during thermal soaring. When thermals were not available, eagles minimized migration time, not energy, by choosing energetically expensive slope soaring instead of waiting for thermals to develop. Sites suited to slope soaring include ridges preferred for wind-energy generation, thus avian risk of collision with wind turbines is associated with evolutionary trade-offs required to maximize fitness of time-minimizing migratory raptors.
Digital Commons Citation
Duerr, Adam E.; Miller, Tricia A.; Lanzone, Michael; Brandes, Dave; Cooper, Jeff; O'Malley, Kieran; Maisonneuve, Charles; Tremblay, Junior; and Katzner, Todd, "Testing an Emerging Paradigm in Migration Ecology Shows Surprising Differences in Efficiency between Flight Modes" (2012). Faculty & Staff Scholarship. 2733.
https://researchrepository.wvu.edu/faculty_publications/2733
Source Citation
Duerr AE, Miller TA, Lanzone M, Brandes D, Cooper J, O'Malley K, et al. (2012) Testing an Emerging Paradigm in Migration Ecology Shows Surprising Differences in Efficiency between Flight Modes. PLoS ONE 7(4): e35548. https://doi.org/10.1371/journal.pone.0035548
Comments
© 2012 Duerr et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.