Testing an Emerging Paradigm in Migration Ecology Shows Surprising Differences in Efficiency between Flight Modes

摘要: To maximize fitness, flying animals should flight speed while minimizing energetic expenditure. Soaring speeds of large-bodied birds are determined by routes and tradeoffs between time costs. Large raptors migrating in eastern North America predominantly glide thermals that provide lift or soar along slopes ridgelines using orographic (slope soaring). It is usually assumed slope soaring faster than thermal gliding because forward progress constant compared to interrupted when pause regain altitude thermals. We tested this slope-soaring hypothesis high-frequency GPS-GSM telemetry devices track golden eagles during northbound migration. In contrast expectations, was slower also were diverted from their migratory path, incurring possible costs reducing towards a endpoint. When thermals, stayed on fast compensated for lack soaring. not available, minimized migration time, energy, choosing energetically expensive instead waiting develop. Sites suited include ridges preferred wind-energy generation, thus avian risk collision with wind turbines associated evolutionary trade-offs required fitness time-minimizing raptors.