Monday, December 07, 2009

Hummingbirds receive spotlight at fluid dynamics meeting

Three scientists recently revealed their findings on hummingbird tongue research at the annual meeting of American Physical Society's Division of Fluid Dynamics in Minneapolis. John W.M. Bush and Francois Peaudecerf of Massachusetts Institute of Technology worked with David Quere of the City of Paris Industrial Physics and Chemistry Higher Educational Institution.

The abstract for their 13-minute talk says:

We present the results of a combined experimental and theoretical investigation of the drinking technique of the hummingbird. Its long, thin tongue is dipped into nectar approximately 20 times per second. With each insertion, fluid rises along the length of the tongue through capillary action.

While the tongue is open in cross-section, resembling a sliced straw, experiments demonstrate that surface tension serves to close it, with the tongue's zipping front corresponding to the rising meniscus. Supporting theoretical and analogue experimental models of this novel, natural example of capillary origami are developed and explored.
The New York Times explains further:

For the latest research, Dr. Bush and his co-workers found that when a hummingbird stuck its tongue into a flower, the tongue, about three-quarters of an inch long, curled up into a cylinder just one twenty-fifth of an inch in diameter because of surface tension.

“The hummingbird’s tongue looks like a straw with a slot cut in it,” Dr. Bush said.

Also because of the surface tension, the slot in the cylindrical tongue zips closed, beginning from the tip. The nectar is drawn upward, and the cylinder fills.
Illustration courtesy of New York Times/Chris Gash

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