Flight performance during hunting excursions in Eleonora’s falcon Falco eleonor

Among birds, falcons are high-performance flyers, in many cases adapted for rial hunting and hence suitable targets for investigating limits to flight performance. Using an optical range finder, we measured flight tracks of Eleonora’s falcon (Falco eleonor ), a species breeding in the Mediterranean region and specialised for hunting autumn passage bird migrants, when commuting between their nesting colony and offshore hunting areas (straight transportation flight) and when searching for prey (transecting and searching flight). Airspeed during searching flight was significantly slower than during straight transportation and transecting flight, but there was no significant difference in airspeed between the latter two flight modes. Straight transportation flight was significantly faster than predicted minimum power speed. Also, during straight transportation flight, the falcons responded to head- and tailwinds by increasing their airspeed when flying into the wind. However, they did not show any significant airspeed adjustments with respect to the angle between the track and the heading, as would be expected in birds trying to maintain a constant track direction. Mean sustainable climb rate (during >240 s) was 1.4