Optimal dynamic soaring trades off energy harvest and directional flight

Wandering albatrosses use dynamic soaring to achieve low-cost, continuous flight over thousands of kilometers. While previous research has primarily focused on energy harvest, directional flight may be more important for reaching a destination. Through numerical simulations validated by flight tracking data, this study reveals a trade-off between maximizing energy harvest and achieving the fastest directional progress: maximizing energy gain increases mechanical energy but slows target-oriented movement, while prioritizing directional flight reduces energy gain. Albatrosses balance this trade-off through a step-selection strategy, dividing each flight cycle into energy-harvest and directional-flight phases, each with distinct priorities. The duration of each phase is influenced by environmental shear strength: low-shear conditions allocate more time to harvest energy, while high-shear conditions favor faster directional movement. By optimizing this balance, albatrosses achieve efficient destination-oriented soaring. These insights enhance our understanding of pelagic bird flight and could inspire high-efficiency robotic albatrosses.