In-flight measurement of upwind dynamic soaring in albatrosses

•Results on upwind dynamic soaring measured at free flying albatrosses are presented.•An analysis of motion, energy and force characteristics is performed.•The physical mechanism underlying the ability of upwind dynamic soaring is shown.•The large-scale upwind movement consists of a tacking type small-scale maneuvering.•The measurement results are based on a high precision GPS-signal tracking method. In-flight measurement results on upwind flight of albatrosses using dynamic soaring are presented. It is shown how the birds manage to make progress against the wind on the basis of small-scale dynamic soaring maneuvers. For this purpose, trajectory features, motion quantities and mechanical energy relationships as well as force characteristics are analyzed. The movement on a large-scale basis consists of a tacking type flight technique which is composed of dynamic soaring cycle sequences with alternating orientation to the left and right. It is shown how this is performed by the birds so that they can achieve a net upwind flight without a transversal large-scale movement and how this compares with downwind or across wind flight. Results on upwind dynamic soaring are presented for low and high wind speed cases. It is quantified how much the tacking trajectory length is increased when compared with the beeline distance. The presented results which are based on in-flight measurements of free flying albatrosses were achieved with an in-house developed GPS-signal tracking method yielding the required high precision for the small-scale dynamic soaring flight maneuvers.