Bio-aerial Locomotion 2011

While hummingbirds are, of course, birds, which make up the Trochilidae family, their aerodynamic characteristics have been more closely attributed to insects.  Not only can the hummingbird hover indefinitely, in midair, it also makes up the only group of birds that possess the ability to fly backwards.  The humming bird, therefore, takes flapping flight to a whole new level.

Depending on the species, the hummingbird can flap its wings anywhere from 8 to 100 times per second.  That’s up to 6,000 times per minute.  However, the hummingbird’s ability to hover is not solely based on how fast it flaps its wings, it also depends on the unique way that the hummingbird flaps its wings.

In most species of birds, the bird depends 100% on the down stroke to generate lift during flapping flight.  These birds, however, do not hover.  Insects, on the other hand, who have mastered the ability to hover, gain 50% of their required lift in the down stroke and 50% in the up stroke of their wing movement.  A study was done by biomechanist, Douglas Warrick of Oregon State University at Corvallis, to determine whether this was in fact the case with hummingbirds.

The main thing that Douglas Warrick and his team set out to do was see what the air looked like in the wake of a hummingbird’s flapping wings.  To achieve this goal, they had rufous hummingbirds hover in place while the “filled the air with a mist of microscopic olive-oil droplets, and shone a sheet of laser light in various orientations through the air around the birds to catch two-dimensional images of air currents.”

This test garnered a number of different discoveries in the way a hummingbird hovers.  Douglas Warrick and his team determined that the hummingbird gets about 75% of its lift from the down stroke and about 25% from the up stroke.  This puts it’s flapping characteristics somewhere in between that of an insect and that of other birds.

They also discovered that while the hummingbird does flap its wings up and down in relation to its body, like most birds, it also holds its body at a much more vertical angle in the air, thus flapping it’s wings from side to side.  The team also noticed that in order for hummingbirds to do this they must, “with each stroke…partially invert their wings, so that the aerofoil points in the right direction.”  This is different from insects who completely turn their wings inside out, the birds’ wings, however, are not this flexible.

So, although the hummingbird does share some aerodynamic characteristics with insects, and with birds, it must remain distinct when it comes to flapping flight.

Sources:

“Hummingbird.” Wikipedia, the Free Encyclopedia. 10 Oct. 2011. http://en.wikipedia.org/wiki/Hummingbird.

“Hummingbirds’ Aerodynamics Are Midway between Insects and Other Birds.” Veterinary Sciences Tomorrow. 10 Oct. 2011. http://www.vetscite.org/publish/items/002289/index.html.