Hummingbirds have long slender bills that allow them to reach deep into flowers to access nectar. Their bills may appear to open when the birds use them to feed, but in fact, a hummingbird’s bill does not actually open.
Anatomy of a Hummingbird’s Bill
A hummingbird’s bill is a long, tapered, slender beak well adapted for accessing liquid nectar from flowers. The two mandibles of the beak are fused together with a slight overlap along their length which allows them to firmly grip flowers as the bird feeds. There are no visible joints or hinges that would allow the bill to open. The bill’s tapered shape and slender proportions give it flexibility to carefully probe into nectar-bearing flowers.
The edge of the mandibles have tiny fringes which allow them to grip and draw nectar up by capillary action. Capillary action refers to the ability of a liquid to flow within narrow spaces, defying gravity, and allows the nectar to travel up the bill as the hummingbird feeds. Inside the bill are grooved tongues with forked tips that can lap up nectar.
While hummingbird bills may appear to open when feeding, this is an illusion created by the rapid motion of the bird plunging its bill in and out of flowers in quick succession. High speed photography reveals their bills do not actually hinge open.
Feeding Behaviors that Create Illusion of an Opening Bill
Hummingbirds have specialized feeding behaviors that allow them to access nectar, the main component of their diet. To drink from flowers, they use their slender bills to reach within blossoms and probe for nectar.
Some of the feeding behaviors that create the appearance of an opening bill include:
- Plunging – Hummingbirds will plunge their bills deep into flower corollas to reach nectar at the base. As they do this, their bill tips may momentarily disappear from view giving the impression they have “opened” inside the flower.
- Lapping – Hummingbirds use their forked tongues to rapidly lap up nectar. Their tongues can flick in-and-out up to 20 times per second. This rapid lapping motion coupled with a plunging bill makes it seem as if the bill is opening and closing.
- Pumping – Hummingbirds sometimes use a pumping motion to draw nectar up into their bills. They will plunge their bill into a flower then pump it back and forth. This pumping action makes it appear as if the bill is repeatedly opening and closing.
- Spreading Mandibles – Hummingbirds can splay their mandibles slightly while feeding to maximize nectar intake. This can create the illusion the two halves of the bill are separating from each other.
While it seems their bills open and close, high speed footage confirms that hummingbird bills stay firmly locked together as they feed with no actual hinging motion occurring.
Why Hummingbird Bills Do Not Need to Open
Hummingbirds have no need for an opening, hinged bill because of the specialized way they feed on liquid nectar. Here are some reasons why an opening bill would not benefit hummingbirds:
- Nectar is a liquid – An opening bill is not required to grasp or bite solid food. Hummingbirds sip nectar which can be drawn into the bill through capillary action without biting or chewing.
- Tongue laps nectar – Hummingbirds use their forked tongues to lap up nectar. There is no need to trap food within the bill, so no need for it to close.
- Long bill reaches nectar – The bill’s length allows it to easily reach nectar at the base of tubular flowers.
- Flexible bill maneuvers into flowers – The slim, tapered bill can flex and maneuver into different shaped flowers.
- Fringed bill edges grip nectar – Fringes along the mandibles allow nectar to adhere through capillary action as it flows toward the tongue.
Since hummingbirds feed exclusively on naturally occurring liquid nectar from flowers, their bills have evolved for optimized nectar access without the need for opening and closing. The slender shape and capillary action work perfectly to draw nectar up without requiring a hinging motion.
Exceptions: Non-Feeding Uses for an Opening Bill
While hummingbird bills do not need to open for feeding, some species can open their bills for other specialized tasks:
- Thermoregulation – Some hummingbird species have been observed gaping or opening their bills wide to facilitate evaporative cooling on hot days.
- Communication – Male hummingbirds may open their bills wide during courtship displays or aggression.
- Predator defense – Young hummingbirds may open their bills instinctively to appear larger and more threatening to potential predators.
So while hummingbird bills do not open for feeding, some species can control bill gaping for other functions like heat regulation, communication, or predator defense.
Conclusion
In summary, a hummingbird’s bill is a specialized nectar extraction tool perfectly adapted for accessing liquid floral nectar. Their long tapered bills do not actually open, despite sometimes appearing to during feeding. Rapid motions like plunging, pumping, lapping, and spreading the mandibles give the illusion of opening, but in reality the upper and lower mandibles remain firmly fused together without hinging joints. Hummingbirds have no functional need for an opening bill, as the slender shape and fringed edges allow nectar to flow into the mouth through capillary action without requiring grasping or chewing motions. While the bill itself does not open, some species can control gaping motions for functions like heat regulation, communication, or predator defense.
