Trans‐oceanic migration and wind utilization by Amur Falcons ( Falco amurensis )

The Amur Falcon Falco amurensis performs one of the world's longest raptor migrations, involving a non‐stop crossing of the Indian Ocean of approximately 2800 km. While the existence of this route is known, the mechanistic details of wind exploitation and seasonal navigation remain to be fully elucidated. We satellite‐tracked seven birds during prebreeding migration of 2010 (six of which arrived at breeding sites), with a subset of three individuals providing data for both directions. One individual was tracked between 2010 and 2013. We analysed the timing of migration resumption and the wind exploitation behaviour during pre‐ and post‐breeding oceanic crossings. We utilized Argos telemetry data and NCEP atmospheric reanalysis data to model flight conditions across isobaric levels and assessed route efficiency by comparing observed tracks with simulated shortest routes and wind‐optimal Correlated Random Walks (CRWs). The estimated wind‐optimal flight altitude was consistently around the 925 hPa level (median 1000‐m prebreeding; 886‐m post‐breeding). The resumption of prebreeding migration was synchronized with high tailwind speeds over the ocean. Prebreeding flights achieved high tailwind assistance (mean: 3.9 m s −1 ), with crossings lasting approximately 60 h. Crucially, we found a significant interaction effect between wind speed and angular deviation, showing that Falcons actively compensated for wind drift, particularly under high crosswind speeds. Consequently, prebreeding tracks remained close to the wind‐optimal routes. In contrast, post‐breeding tracks exhibited lower tailwind speeds (mean: 3.2 m s −1 ) over longer durations (~78 h), and showed increased drift tolerance. The Falcons' navigational success depends on a highly flexible, seasonally dependent interaction between wind conditions and route control, suggesting a state‐dependent strategy rather than simple drift. The prebreeding crossing is highly optimized for time minimization, while the post‐breeding phase appears less constrained. The reliance on specific wind corridors renders this unique migratory system potentially vulnerable to climate‐driven changes in large‐scale atmospheric patterns.