Wandering abatross flight data

Wandering albatrosses exploit wind shear by dynamic soaring, enabling
rapid, efficient, long-range flight. To explore this flight mode, we
compared the ability of a nonlinear dynamic soaring model and a linear
empirical model to explain observed variation of the airspeeds of
GPS-tracked albatrosses in across-wind flight. In fast winds (> 8
m/s), maximum observed airspeeds reach an asymptote at ~ 20 m/s, whereas
the dynamic soaring model predicts much faster airspeeds, up to around 50
m/s. We hypothesize that the birds actively limit airspeed by making
fine-scale adjustments to turn angles and soaring heights. Predicted
dynamic soaring airspeeds do not extend down to the slowest winds
(< 3.2 m/s) of observed flight. We hypothesize that in slow winds
wandering albatrosses obtain additional energy from updrafts over water
waves. The dynamic soaring model predicts that the minimum wind speed
necessary to support dynamic soaring at a cruise airspeed of 16 m/s is 3.2
m/s, achieved via a flight trajectory of linked 137° turns. In reality,
observed turn angles are typically ~ 60°. Our simulations suggest that
birds may necessarily use smaller turns angles than the theoretical
optimum for fast flight in order to limit aerodynamic force on their
wings.