Observations and models of across-wind flight speed of the wandering albatross

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Date
2022-11-30
Authors
Richardson, Philip L.
Wakefield, Ewan D.
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DOI
10.1098/rsos.211364
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Wind shear
GPS tracking
Dynamic soaring
Wandering albatross
Flight trajectory
Airspeed
Abstract
Wandering albatrosses exploit wind shear by dynamic soaring (DS), enabling rapid, efficient, long-range flight. We compared the ability of a theoretical nonlinear DS model and a linear empirical model to explain the observed variation of mean across-wind airspeeds of GPS-tracked wandering albatrosses. Assuming a flight trajectory of linked, 137° turns, a DS cycle of 10 s and a cruise airspeed of 16 m s−1, the theoretical model predicted that the minimum wind speed necessary to support DS is greater than 3 m s−1. Despite this, tracked albatrosses were observed in flight at wind speeds as low as 2 m s−1. We hypothesize at these very low wind speeds, wandering albatrosses fly by obtaining additional energy from updrafts over water waves. In fast winds (greater than 8 m s−1), assuming the same 10 s cycle period and a turn angle (TA) of 90°, the DS model predicts mean across-wind airspeeds of up to around 50 m s−1. In contrast, the maximum observed across-wind mean airspeed of our tracked albatrosses reached an asymptote at approximately 20 m s−1. We hypothesize that this is due to birds actively limiting airspeed by making fine-scale adjustments to TAs and soaring heights in order to limit aerodynamic force on their wings.
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© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Richardson, P. L., & Wakefield, E. D. Observations and models of across-wind flight speed of the wandering albatross. Royal Society Open Science, 9(11), (2022): 211364, https://doi.org/10.1098/rsos.211364.
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Richardson, P. L., & Wakefield, E. D. (2022). Observations and models of across-wind flight speed of the wandering albatross. Royal Society Open Science, 9(11), 211364.
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