Hummingbirds possess an oral cavity, or mouth, housed within their highly specialized bill. This feeding apparatus is a unique adaptation that allows these tiny flyers to sustain their extremely high metabolic rate. Hummingbirds are specialized feeders that rely primarily on high-energy floral nectar, but they also require small insects for protein.
The Structure of the Hummingbird Bill
The hummingbird’s bill is a long, slender, and finely tapered extension of the head. It is composed of bone covered by keratin, the same material found in human fingernails. The bill functions primarily as a protective sheath for the specialized tongue and as a tool to probe deep into flowers.
The upper mandible generally overlaps the lower mandible slightly at the tip, which makes the bill appear completely closed. Hummingbirds possess considerable control over their mandibles, and the flexible lower mandible aids in fine control during feeding. The bill’s length and curvature often co-evolved with the specific flowers the bird feeds on, maximizing nectar extraction.
The Specialized Hummingbird Tongue
The tongue is the most remarkable feature of the feeding system, allowing the bird to reach nectar far beyond the bill’s tip. It is not a simple straw, but a muscular and elastic organ that is forked toward the end. The edges of the two tips are rolled inward, forming two tiny micro-channels that run along the tongue’s length.
These channels feature small, hair-like fringes, sometimes called lamellae, that unfurl when the tongue is extended into liquid. The tongue’s immense reach is made possible by the elongated hyoid apparatus, a bone structure. This apparatus is so long that when the tongue is fully retracted, the hyoid bones wrap back under the jaw and extend over the top of the skull. This arrangement allows the tongue to extend a distance roughly equal to the length of the bill itself.
How Hummingbirds Drink Nectar
The mechanism by which hummingbirds drink nectar is a dynamic, high-speed action relying on the unique structure of the tongue. The bird does not suck the liquid or draw it up through simple capillary action. Instead, the tongue is extended and retracted rapidly in a piston-like lapping motion.
This lapping action can occur at an astonishing rate, sometimes reaching 15 to 20 flicks per second. As the forked tips of the tongue touch the nectar, the micro-channels open to trap the fluid. When the tongue is retracted, the channels compress, bringing the nectar to be swallowed.
This highly efficient method ensures the bird can quickly consume the large quantities of sugar needed to fuel its active lifestyle. The bill is also used to capture small arthropods like spiders and insects, which provide the necessary proteins.