Tongue of the Hummingbird

photo: Dr. Kristiina Hurme

A hummingbird’s feeding mechanism is a rapier-like bill protecting a tongue that has adapted to extend deep into flowers to drink pools of sugar-rich nectar.

Conventional wisdom among ornithologists held that a hummingbird’s tongue used capillary action to draw in the nectar. Capillary action, or wicking, describes liquid flowing into narrow spaces due to intermolecular forces, rather than some external forces like gravity.

This past summer, while hummingbirds in North America were gathering nectar in preparation for their migratory journey to equatorial locations, evolutionary biologist and functional morphologist Alejandro Rico-Guevara published the results of a study that suggests the hummingbird’s tongue acts like an elastic micro-pump.

The hummingbird’s tongue acts like an elastic micro-pump.

Rico-Guevara observed that hummingbirds can draw nectar from a flower in less than a second which, he reasoned, was much too quick to be attributed to the wicking action of intermolecular forces. Rico-Guevara’s study suggest that the hummingbird’s tongue is compressed as it approaches the nectar, then becomes plump as the nectar rapidly hydrates grooves in the tongue.

Rico-Guevara’s slow-motion video posted on YouTube by Science News shows a hummingbird repeatedly extending its tongue into a red drink.

And the humming-bird that hung
Like a jewel up among
The tilted honeysuckle horns
They mesmerized and swung
In the palpitating air,
Drowsed with odors strange and rare.
And, with whispered laughter, slipped away
And left him hanging there.
James Whitcomb Riley

REFERENCES


Originally published at essays.grokearth.com on October 17, 2015.

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