The tongue of a hummingbird is even more complex than I imagined. Its tongue is twice the length of its bill and is a V-shaped fork with hairs in the inner edges. Initially it was thought to act as a long straw to suck up nectar by capillary attraction. Research from University of Connecticut in 2011 reversed this finding. They studied 20 hummers postmortem and made videos of 10 different species feeding. As explained at Phys.org:
"The hummingbird has a forked tongue which is lined with hair-like extensions called lamellae. When inside the flower, the tongue separates and the lamellae extend outward. As the bird pulls its tongue in, the tips come together and the lamellae roll inward. This action traps the nectar within the tongue."Even more amazing is the fact that it requires no energy to use the tongue. Postmortem studies with videos at Phys.org showed the tongues of dead birds retracting the same way. This saves a lot of energy when you consider that a hummingbird's tongue can take 20 "sips" a second! Think what they could do in a chug-a-lug contest. You can see it in action in this video.
Eating a dish of hummingbird tongue has been quoted as a sign of the ultimate profligate society such as some Roman Emperors created. No wonder the Roman Empire collapsed. Their leaders must have starved.