In a study published Wednesday in the journal Proceedings of the Royal Society B: Biological Sciences, researchers uncovered the truth: Their tongues work like tiny mechanical pumps.
Study authors Alejandro Rico-Guevara and Kristiina Hurme (both of the University of Connecticut) explained the process in an article for the Conversation:
The grooves in the hummingbird tongue don’t reach the throat, so the bird cannot use them as tiny straws. For this reason, instead of using vacuum to generate suction – imagine drinking lemonade out of a straw – the system works like a tiny pump, powered by the springiness of the tongue. The bird squashes the tongue flat, and when it springs open, this expansion rapidly pulls the nectar into the grooves in its tongue. It turns out it’s elastic energy – potential mechanical energy stored by the flattening of the tongue – that lets hummingbirds collect nectar much faster than if they relied on capillarity.
In other words, the bird rapidly reshapes its tongue, and that change in tension draws sweet nectar into their mouths.
This allows them to drain an entire flower in under a second — a process much too quick for capillary action.