The long, slender bill of the hummingbird, perfectly shaped for probing deep into tubular flowers, often leads people to question its flexibility. While this specialized tool appears rigid, hummingbirds are capable of opening their beaks much wider than they do while feeding on nectar, especially at the base. This ability to expand their mouths is a necessary adaptation for their varied diet and complex behaviors, making the bill a versatile instrument.
The Mechanics of the Gape
The hummingbird’s ability to open its mouth wide involves a kinetic skull structure. The upper part of the beak (maxilla) can be slightly raised, but the most significant movement comes from the lower mandible. The two halves of the lower jaw are not rigidly fused near the throat, allowing them to flex outward and downward. This mandibular bending increases the circumference of the mouth opening near the bird’s head. While the tip of the bill remains stiff, the base provides the necessary mechanical expansion for a surprisingly large gape.
Nectar Collection: The Role of the Tongue
When drinking, the hummingbird does not need to open its bill widely, only enough to allow its specialized tongue to extend. High-speed video studies show the tongue does not function like a straw to siphon nectar. Instead, the tongue is forked at the tip and features tiny, fringed edges called lamellae. The bird rapidly protrudes and retracts this tongue, sometimes exceeding 13 licks per second, to collect the sugary liquid. The tongue works as an elastic micropump: the two grooves on the tip collapse as they are retracted through the bill, squeezing the nectar into the mouth. When extended, the grooves spring open due to elastic recovery, drawing the fluid in at a high speed. This rapid lapping action is highly efficient for fueling the bird’s extreme metabolism.
Insect Hunting and Aerial Gaping
Hummingbirds require protein and other nutrients, which they obtain by consuming small arthropods through a method known as hawking. This secondary feeding method demands the full use of the bird’s gape flexibility. The bird must open its mouth wide and fast to capture gnats, spiders, and tiny flies mid-flight or from foliage. During these hunting maneuvers, the lower jaw flexes laterally and ventrally, maximizing the mouth opening to create an effective net for prey capture. Widening the gape compensates for the bill’s long, narrow shape, allowing for a rapid, elastic snap-closure to secure the insect.
Other Functions of the Beak
The hummingbird’s bill is used for several survival and social activities beyond feeding.
Non-Feeding Uses
- Preening: The bill is used to smooth feathers, maintaining flight efficiency and insulation.
- Territorial disputes: Males use the bill for aerial fencing, jabbing at rivals to defend feeding sites or mates.
- Nest construction: The bill aids in gathering and weaving fine materials like plant fibers and spider silk into a secure home.
- Communication and thermoregulation: The bird must open its mouth to produce vocalizations and to perform evaporative cooling, similar to panting, on hot days.