How Hummingbirds Get Their Nectar With Tiny ‘Straws’

[Donna]

How Hummingbirds Get Their Nectar With Tiny ‘Straws’


It is harder to suck liquid through a thin straw than a wider one because of viscosity.
Yet a hummingbird is able extract nectar from a flower by wrapping its tongue into a hummingbird-size straw. How?

The answer is that the hummingbird is taking advantage of the forces of surface tension, the same forces that cause water to bead into droplets instead of spreading outward when sitting on a hard surface.

“I’ve been looking at the big picture of drinking strategies in nature,� said John W. M. Bush, a professor of applied mathematics at the Massachusetts Institute of Technology. “This is a big theme of mine now.�

Last year, he showed how some shorebirds used surface tension to draw water droplets up their long, thin beaks into their mouths.

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.

The hummingbird then scrapes its tongue clean and swallows. Amazingly, it repeats this process 20 times a second as it feeds.

The hummingbird tongue research, which Dr. Bush presented on Sunday at a meeting of the American Physical Society’s Division of Fluid Dynamics, is not just a biological curiosity.

The findings could be useful to researchers building miniature chemistry laboratories — so-called labs on a chip — that have to move tiny droplets of chemicals around.

“Nature has already solved these problems,� Dr. Bush said.

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