Hummingbirds or Hummingbugs?

A small hummingbird zipping by on its way to a flower could easily be mistaken for a large flying insect. And for good reason--researchers have found that hummingbirds fly more like insects than other birds.

After strategically placing nine tiny dots of non-toxic paint on a Ruby-throated Hummingbird's wing, researchers were able to precisely track the hummingbirds' rapid flight movement with a high-speed camera. They then used the data on the positions of these nine points to construct a precise three-dimensional simulation, according to a study published last week in Journal of the Royal Society Interface.

"Hummingbirds are more like insects in flight techniques in the sense that they can perform hovering and slow-speed flight," says researcher Haoxiang Luo, assistant professor of mechanical engineering at Vanderbilt University.

With birds, insects, or even airplanes, a physical force known as lift is key to flight. The lift force, created by a flow of air that forms a vortex, pushes the flier upward. In the case of birds and insects, beating their wings creates the vortices, which in turn yield lift.

For insects, lift is generated by both the upstroke and the downstroke. Birds, on the other hand, generate nearly all of their lift force on the downstroke--with the exception of hummingbirds.

As the above video shows, hummingbirds actually invert their wings on the upstroke. This action creates a vortex of air that contributes to the lift force that allows them to hover.

(In the first simulation seen in the video, the red spirals represent the vortices, and you can see how opposite sides of the birds' wings turn red as they beat. In the second simulation, the same process occurs in blue.)

Engineers are paying attention to this complex flight technique in part because it could help them build better micro air vehicles, such as the "Nano Hummingbird."