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By NICHOLAS BAKALAR
Published: May 2, 2011
Since the theory was first put forth in 1833, ornithologists have assumed that hummingbirds drink by capillary action: The bird curls its forked tongue into a straw shape, and the liquid is drawn up the tube by surface tension.
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Alejandro Rico-Guevara
The forked tongues of hummingbirds have tips lined with hairlike extensions called lamellae.
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“Someone decided this, and no one has really changed their mind since,” said Margaret A. Rubega, an associate professor of ecology at the University of Connecticut. Now she and Alejandro Rico-Guevara, a graduate student at the university, report in The Proceedings of the National Academy of Sciences that it is not that simple.
Using a high-speed video camera, the researchers photographed 30 hummingbirds of 10 species as they drank from a feeder. They also did postmortem microscopic examinations of the tongues of 20 additional birds. Their report was posted online Monday.
The edges of a hummingbird’s tongue are lined with lamellae, a fringe of hairlike fleshy extensions. The tongue is wet when it encounters the nectar, the tongue’s two tips are tightly closed, and the lamellae are flattened against it. Then the tip of the tongue separates and the lamellae extend from each fork. As the bird pulls its tongue in past the surface of the liquid, the tongue tips come together, and the lamellae roll inward, trapping the nectar. At that point, Dr. Rubega said, capillary action probably moves the liquid into the throat.
The researchers found the same process when they a manipulated the tongues of dead birds. This means it requires no additional energy on the part of the bird — pulling the tongue past the surface of the liquid is enough to catch the nectar.
“The tongue is less than one millimeter thick,” said Mr. Rico-Guevara. “And it’s hidden inside a flower. But you use flat-sided feeders to avoid distortion, and you can see what happens. It’s amazing.”
This article has been revised to reflect the following correction:
Correction: May 4, 2011
A report in the Observatory column on Tuesday about the drinking technique of hummingbirds misstated the size of a hummingbird’s tongue, using information provided by a University of Connecticut researcher. It is less than one millimeter thick, not less than one millimeter long.
Published: May 2, 2011
Since the theory was first put forth in 1833, ornithologists have assumed that hummingbirds drink by capillary action: The bird curls its forked tongue into a straw shape, and the liquid is drawn up the tube by surface tension.
Enlarge This Image
Alejandro Rico-Guevara
The forked tongues of hummingbirds have tips lined with hairlike extensions called lamellae.
Multimedia
How Hummingbirds Drink
Related
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Get Science News From The New York Times » “Someone decided this, and no one has really changed their mind since,” said Margaret A. Rubega, an associate professor of ecology at the University of Connecticut. Now she and Alejandro Rico-Guevara, a graduate student at the university, report in The Proceedings of the National Academy of Sciences that it is not that simple.
Using a high-speed video camera, the researchers photographed 30 hummingbirds of 10 species as they drank from a feeder. They also did postmortem microscopic examinations of the tongues of 20 additional birds. Their report was posted online Monday.
The edges of a hummingbird’s tongue are lined with lamellae, a fringe of hairlike fleshy extensions. The tongue is wet when it encounters the nectar, the tongue’s two tips are tightly closed, and the lamellae are flattened against it. Then the tip of the tongue separates and the lamellae extend from each fork. As the bird pulls its tongue in past the surface of the liquid, the tongue tips come together, and the lamellae roll inward, trapping the nectar. At that point, Dr. Rubega said, capillary action probably moves the liquid into the throat.
The researchers found the same process when they a manipulated the tongues of dead birds. This means it requires no additional energy on the part of the bird — pulling the tongue past the surface of the liquid is enough to catch the nectar.
“The tongue is less than one millimeter thick,” said Mr. Rico-Guevara. “And it’s hidden inside a flower. But you use flat-sided feeders to avoid distortion, and you can see what happens. It’s amazing.”
This article has been revised to reflect the following correction:
Correction: May 4, 2011
A report in the Observatory column on Tuesday about the drinking technique of hummingbirds misstated the size of a hummingbird’s tongue, using information provided by a University of Connecticut researcher. It is less than one millimeter thick, not less than one millimeter long.