By Susan Milius
A new way of looking at hummingbird tongues sees them mainly as long, skinny pumps.
This view challenges an old notion of how hummingbirds sip — that nectar flows up open grooves in the tongue the way water rises inside thin capillary tubes, says functional morphologist Alejandro Rico-Guevara of the University of Connecticut in Storrs. It’s the latest in a lively debate over just how hummingbird tongues work.
The “elastic micropump” theory that Rico-Guevara and his Connecticut colleagues propose relies on the same tendency of water molecules to grip each other that creates capillary rise up an open tube. But Rico-Guevara’s high-speed videos show that hummingbirds in the wild rarely dip open grooves into nectar. Instead, bird bills squash the tongue and its grooves flat. When the tongue tip touches nectar, the grooves spring open, pulling up a column of nectar as they expand. This pulling, or pumping, slurps nectar faster than grooves that stayed open would, the researchers report online August 19 in the Proceedings of the Royal Society B.