[Slow motion of a Philippine eagle in flight. It flaps its wings twice, then glides. The tips of its wings curve upward. Then it flaps many more times before soaring for a longer period. Next it flaps four times before gliding. It flaps again and disappears behind a tree. It becomes visible again, gliding, before briefly disappearing behind another tree. It is still gliding when it reappears.] [Bird call]

End of transcript

To understand the unique flight styles of different bird species, scientists use a technique called wing tracing. It involves tracing the trajectory of a point on their wing during a series of wingbeats. The pattern of a bird’s wingbeat depends on how far a bird can move its wing in any given direction, which is determined by the length and shape of the wing. Soaring birds such as this Philippine Eagle, show an elliptical shaped wingtip path when viewed from the side.

This video accompanies Chapter 5, Avian Flight, Handbook of Bird Biology, 3rd Edition from the Cornell Lab of Ornithology and Wiley Publishing.

Recorded by Neil Rettig