Essays: Tongue of the Hummingbird

Saturday, October 17, 2015

Tongue of the Hummingbird

Exposed tongue of a
black-throated mango
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 the hummingbird's tongue used capillary action to draw in nectar. Capillary action 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 locales, 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.

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 slow-motion video posted on YouTube by Science News (above) shows a hummingbird repeatedly extending its tongue into a red drink.

The hummingbird's tongue acts like an elastic micropump.

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.

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

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