Wind driven effects on the fine-scale flight behaviour of dynamic soaring wandering albatrosses

Abstract

Wandering albatrosses Diomedea exulans are among the largest flying birds. Their energy-efficient dynamic soaring flight allows them to travel large distances by exploiting the gradient in wind strength above the sea surface. We used bio-logging devices to study the dynamic soaring flight behaviour of wandering albatrosses, deriving roll (bank) angles from video and tri-axial magnetometers, and flapping events from tri-axial accelerometers. Albatrosses mostly experienced westerly winds coming from their left during outbound flights from their colonies and from their right when returning. They compensated for differences in wind speed by varying their roll angles and predominantly turning into the wind, resulting in a net displacement that was perpendicular to the wind. Flapping flight was influenced by wind speed and direction, with birds spending more time flapping in light winds and in head winds. Flapping often occurred at the upper turn of the dynamic soaring cycle, a stage previously considered devoid of flapping. There was also evidence of sexual differences in flight behaviour, with females flapping less than males. Males almost exclusively take off into head winds, whereas females utilized cross winds as well. These results add to our knowledge of dynamic soaring and show how albatrosses react to their wind fields at a fine scale.