Hummingbirds operate at high speed, with a heart that beats more than 1,000 times per minute and wings that beat up to 50 times per second. When scientists slowed down footage of their tongues sucking up nectar, they found that an incredibly fast behavior is at play here, too.
In less than a tenth of a second, hummingbirds employ a clever pumping mechanism at the tip of their tongue, researchers report in the journal Proceedings of the Royal Society B. To figure out how exactly the tiny pumps work, biologists teamed up with experts in fluid mechanics.
"Our research shows how they really drink and provides the first mathematical tools to accurately model their energy intake, which will in turn inform our understanding of their foraging decisions and ecology," lead researcher Alejandro Rico-Guevara said in a statement.
Up until this study, the prevailing idea was that hummingbirds took advantage of a property of liquids called capillary action. This allows liquids to climbs up the walls of narrow crevices, against the force of gravity.
Since a hummingbird's tongue is thinner than fishing line, this seemed like a plausible explanation. However, the high-speed video revealed that hummingbirds are actively driving the flow of nectar toward their bills rather than passively relying of the properties of the liquid itself.
Hummingbird tongues fork into two tiny tubes at the end. When the hummingbird sticks its tongue down into a flower's nectar, it squeezes the tubes so that they open up when they hit the nectar and fill with liquid. The energy that the hummingbird used to press its tongue flat gets stored in the elastic walls of the tube and powers the pumping of the nectar.