Seabird trajectories map onto a reduced optimal-control bound for dynamic soaring.

Area of Science:

• * Biomechanics and animal flight dynamics.
• * Ornithology and avian locomotion.
• * Optimal control theory in biological systems.

Background:

• * Dynamic soaring enables seabirds to exploit wind shear for energy, but a standardized performance benchmark is lacking.
• * Existing flight analysis methods do not adequately compare species with different flight strategies (e.g., dynamic soaring, flap-gliding).

Purpose of the Study:

• * To establish a reduced benchmark for comparing flight performance across avian species utilizing wind energy.
• * To analyze and compare the flight efficiency of wandering albatrosses, Cory's shearwaters, and Eurasian oystercatchers.

Main Methods:

• * Developed a simplified optimal-control model (Hamilton-Jacobi-Bellman) to define a lower bound on transport effort, considering drag and wind subsidies.
• * Normalized flight speed and used accelerometer data as an effort proxy for species-specific comparisons.
• * Mapped flight data onto a reduced speed-effort plane to estimate empirical performance frontiers.

Main Results:

• * Wandering albatrosses exhibited flight efficiency closest to the theoretical lower bound, indicating near-optimal wind-energy harvesting.
• * Cory's shearwaters showed a performance frontier systematically above the bound, suggesting less optimized energy use.
• * Eurasian oystercatchers operated in a distinct non-soaring flight regime.

Conclusions:

• * The developed framework provides a unified mechanical representation for comparing dynamic soaring, flap-gliding, and non-soaring flight.
• * This study offers a novel benchmark for assessing wind-assisted flight performance across diverse avian species using field trajectory data.