Planet Earth

Hummingbirds Are Not Sipping Straws. They're Doing Something Much Weirder.

80beatsBy Veronique GreenwoodMay 4, 2011 6:43 PM

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What’s the News: Hummingbirds have been keeping a secret, now revealed by high-speed videos: their tongues are nothing like straws. They’re much more like mops. Those dexterous helicopters of the sky (and mascots of this fine news aggregator) are known for consuming large quantities of flower nectar—as much as 14 times their body weight in a day—to power their speedy metabolisms (when your heart beats more than 1,200 times a minute, you’ve got to keep gobbling that fuel). Researchers had always thought that hummingbird tongues, which are forked, functioned like a coffee straw, with two slender tubes using capillary action—the force pulling liquid up the sides of a tube—to drink. But new video evidence shows the two halves of hummingbird tongues scooping up the fluid like tiny hands, knocking the straw theory out of the running. How the Heck:

  • According the physics of capillary action, hummingbirds should be drawn to thinner, more fluid food. But consistently, they prefer the thicker stuff. This was baffling to biologists, until a team published new high-speed movies showing tongues in action.

  • The team built transparent “flowers,” filled them with sugar water, and filmed with high-speed, high-magnification cameras as hummingbirds came to feed.

  • What they saw (see video above), was nothing short of astounding: the two halves of the tongue shoot into the water and scoop it together like the hands of swimmer, sopping up the fluid with thin hairs called lamellae that line the tongue, then clamp together to seal it in. They watched 30 hummingbirds of 10 species, and all used this method to feed.

  • What’s more, even the tongues of dead hummingbirds will whip out and sop up fluid, the researchers found, indicating that the process doesn’t require any energy input from the bird.

The Future Holds:

  • This discovery doesn’t just rewrite the books on how hummingbirds work, it also suggests new avenues for biomimicry in design. The way the bird sops up fluid could be studied to develop more absorbent materials, or even aid in designing fluid-sipping robots where the thickness of a fluid makes capillary action infeasible.

  • For the researchers, their next goal is figuring out how the bird extracts and swallows the fluid from the tongue, a process for which they’ll pull out more high-tech imaging gear, including CT scans, they tell Wired Science.

Reference: Alejandro Rico-Guevara1 and Margaret A. Rubega. The hummingbird tongue is a fluid trap, not a capillary tube. Published online before print, May 2, 2011. doi:10.1073/pnas.1016944108Video credit: Alejandro Rico-Guevara/University of Connecticut

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