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

• Published in: Royal Society Open Science
• Main Authors: Richardson, Philip L., Wakefield, Ewan D.
• Other Authors: UK Natural Environment Research Council, Woods Hole Oceanographic Institution emeritus fund
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2022
• Subjects: Multidisciplinary; Wandering Albatross
• Online Access: http://dx.doi.org/10.1098/rsos.211364; https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.211364; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsos.211364

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.