Aerodynamic limits of gliding flight in grey-headed albatrosses under variable wind conditions

Abstract

Adult grey-headed albatrosses breeding on Marion Island experience highly variable near-ground wind vectors that can result in crash landings, some of which are fatal. This study quantifies the combinations of airspeed and wind direction that can lead to loss of lift or the generation of downforce sufficient to cause such crashes. Using a previously developed three-dimensional grey-headed albatross body geometry, we conducted numerical simulations of this rigid geometry across a wide range of flight conditions defined by airspeed, angle of attack, and sideslip angle. Lift and aerodynamic efficiency (lift-to-drag ratio) are then evaluated to identify conditions under which insufficient lift is produced. Simulations show that for airspeeds below 10 m·s⁻¹, the generated lift is lower than the average weight of an adult grey-headed albatross, with peak aerodynamic efficiency occurring at an angle of attack of approximately 5°. While the geometry generates lift effectively under either strong crosswinds or downdrafts alone, their combination can produce substantial downforce. Given that albatrosses preferentially exploit crosswinds at the meso-scale, transient gusts combining crosswind and downdraft components may force birds into the ground, particularly during low-altitude nest departure, increasing the likelihood of fatal crash landings.