Physics Photo of the Week

August 31, 2012

Hummingbird Flight

Hummingbirds exhibit the amazing ability to hover when sipping nectar from flowers and back-yard bird feeders.  Notice that this bird's wings appear to be backwards!  The leading edge of its wings - the roots of the feathers - is behind the feathers.  This is because the wing  during hovering moves horizontally back and forth, not up and down as in forward flight.  The hummingbird in the photo is executing the wing's return stroke; the bird has rotates its wing bone (humerus) in its shoulder socket so that the leading edge of the wing alternately faces the rear and front during the complete wing stroke.

In the animated sequence at right one can see that the wings are rotated alternately forward and back for the forward and backward strokes respectively.  In both halves of the wingstroke, the feathers point downward at an angle to give lift.  In the final few frames of the high-speed video clip the hummingbird changes the pitch of its left wing in order that the left wing gives some forward thrust and the bird begins to fly off to the right.

Compare the hummingbird flight with that of the bumblebee (Physics Photo of the Week for April 8, 2011).  The technique of rotating the wings with the return strokes is the same for both animals.

Hovering is very "expensive" for flying animals - mainly because all the lift must be produced by the wing motions.  Birds ordinarily obtain a significant lift merely from their forward motion through the air.  Only the smallest flying animals can hover for any appreciable length of time.


Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

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