STORRS, Conn., Aug. 19 (UPI) — Until now, researchers thought a hummingbird’s tongue retrieved nectar by “wicking” — a capillary action whereby liquid flows through a narrow tube without the assistance or influence of gravity.
But a team of scientists at the University of Connecticut have overturned the wicking theory. After studying 18 different hummingbird species feeding in the wild, using special high-speed cameras, researchers concluded hummingbird tongues act as tiny pumps.
The tongue is flattened by the bird’s beak, and can be seen in slow-mo replay to be collapsing prior to reaching the nectar. As the tip hits the nectar, the tube erects and inflates as it fills. When the hummingbird pinches and squeezes the liquid from its tongue, it once again collapses the tubes, loading elastic energy and facilitating a pumping action that draws more nectar.
The entire pumping action happens within the span of a tenth of a second.
The researchers had the video proof, but they also wanted a mathematical explanation. It was skepticism over the limited rate at which wicking would allow the hummingbirds to extract nectar that first led them to reexamine the tongue’s mechanics.
“We could see the actual drinking mechanism through high speed video, but we couldn’t develop the fluid dynamics model needed to test our biophysical hypothesis,” research scientist Alejandro Rico-Guevara explained in a press release.
The scientists teamed up with experts in fluid mechanics and tested a variety of hypotheses on paper. Ultimately, the team was able to confirm the physics behind their micro-pumping explanation.
The mathematical details were published this week in the journal Proceedings of the Royal Society B: Biological Sciences.
“Our research shows how they really drink and provides the first mathematical tools to accurately model their energy intake,” said Rico-Guevara, “which will in turn inform our understanding of their foraging decisions and ecology.”
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