WHY DO YOU CALL THEM STORM PETRELS? MECHANICS OF SEA-ANCHOR SOARING

摘要

This study presents a concise mathematical model that accounts for sea-anchor soaring, a special flight technique used by sea birds, in particular storm petrels. Conventional wing theory is used to reveal the mechanics of sea-anchor soaring. The feasibility and existence of an equilibrium are summarized by formulae giving the wind velocity criteria. The stability of the equilibrium is also revealed: among two possible equilibria, the equilibrium at the very slow velocity to water is shown to be stable. Numerical results show the following: sea-anchor soaring is almost always stable; foot-web size regulates the size of a bird using sea-anchor soaring at low velocities to water.