The Wake of a Kestrel (Falco Tinnunculus) in Gliding Flight

The wake of a kestrel gliding down a 36 m long corridor was examined using multiple-flash stereo photographs of small bubbles of helium in soap solution. Qualitatively and quantitatively, the wake is very similar to that which would be measured behind an elliptically loaded aerofoil of the same span. The significance of this close agreement with classical aerodynamic theory is briefly discussed and the results are compared with others measured or assumed in the bird flight literature.