Hummingbirds are well known for their unique method of feeding – using their long tongues to drink nectar from flowers. Their tongue has evolved into a highly specialized tool that allows them to access sugars from blossoms in a way that few other animals can. But is their tongue actually hollow on the inside? Let’s take a closer look at the anatomy and function of the hummingbird tongue to find out.
Quick Answer
Yes, a hummingbird’s tongue is hollow. The tongue contains two thin tubes running down the length which allows nectar to move through capillary action. This hollow tube structure, along with tiny fringed edges on the tongue, allows hummingbirds to efficiently lap up liquid nectar.
Anatomy of the Hummingbird Tongue
The hummingbird tongue consists of two tubes fused together into one organ. The outer edges of the tubes have branched filaments called lamellae. When the tongue goes into a flower, the lamellae flare out, increasing surface area. This allows the tongue to capture more nectar.
Inside each tube is a thin rod of elastic tissue. This fills with blood to stiffen the tongue during feeding. The rods are retracted when the tongue is not in use, allowing it to curl inside the bill.
Nectar moves through the hollow tubes via capillary action. The nectar gets drawn into the tubes without any effort from the hummingbird. So even though their tongues go in and out 13-17 times per second, they don’t have to exert energy to suck up nectar.
Why a Hollow Tongue?
A hollow tube tongue provides two main advantages for hummingbirds:
- Increased surface area – The branched filaments along the tongue provide a larger surface area for nectar collection. More nectar sticks to the tongue on each lick.
- Efficient fluid movement – The hollow tubes allow nectar to move through capillary action without expending energy. This passive fluid transport is faster and less tiring than sucking.
Together, these factors allow hummingbirds to feed at a high rate. They can lap up to 13 times per second, maximizing the amount of energy gained from each flower.
How the Hollow Tongue Works
When feeding, the hummingbird will insert its tongue into a flower. The branches along the edge flare out to increase surface contact. Nectar adheres to the tongue by cohesion and surface tension.
The nectar gets drawn into the hollow tubes passively by capillary action. As the liquid encounters the small diameter tubes, adhesion and cohesion draw it upwards. This wicking effect causes the nectar to rapidly fill the tubes.
Once the tongue is retracted, contractions of the tongue muscles squeeze the tubes, pushing the nectar back to the throat. The elastic tissue rods provide rigidity when extended out of the bill, but relax to allow the tubes to be compressed.
This cycle repeats about every 0.07 seconds, allowing hummingbirds to exploit flower nectar at high repetition rates. The process requires little energy input from the bird – the tongue anatomy does most of the work.
Evolutionary Adaptations
The specialized hummingbird tongue reflects evolutionary adaptations for nectivory. Key adaptations include:
- Elongated tongue – Can extend up to twice the length of the bill to reach nectar.
- Fringed edges – Increase surface area for nectar collection.
- Grooved surface – Helps spread nectar across the tongue surface through capillary action.
- Protractile sections – Allow the tongue to dart in and out of flowers quickly.
These traits enable hummingbirds to feed on flower shapes not accessible to other birds. Their feeding method is highly efficient, gaining 25-33% of their body mass in nectar daily.
Challenges of Feeding
While the tongue anatomy is optimized for nectar feeding, hummingbirds still face challenges:
- Nectar viscosity – Thicker nectars are harder to draw up into the tubes.
- Tongue flexibility – Stiffness from drying nectar can reduce tongue maneuverability.
- Flower shape – Long or curved blossoms are more difficult to access.
- Competition – Other pollinators lower nectar availability.
Hummingbirds have evolved feeding strategies to help overcome these issues. For example, they will shake their heads while feeding to help move viscous nectar into the tongue tubes. They are also territorial and will aggressively defend flower resources.
Comparison to Other Bird Tongues
| Bird Group | Tongue Structure | Feeding Adaptations |
|---|---|---|
| Hummingbirds | Long, hollow tubes with fringed edges | Specialized for nectar feeding |
| Woodpeckers | Long, spear-shaped, barbed tip | Extracting insects from wood |
| Parrots | Short, thick, fleshy | Cracking hard nuts/seeds |
| Penguins | Spiny, with backward-facing hooks | Catching slippery fish |
The hummingbird tongue is highly specialized for gathering floral nectar. Their unique hollow tube adaptation allows them to exploit a food source other birds cannot access.
Unusual Feeding Methods
While nectar is their primary food, hummingbirds have some unusual feeding methods as well:
Insect Eating
Hummingbirds will supplement their diet with small insects for extra protein. They catch insects on the wing or pull them from spider webs and branches. Their broad tongue tip helps trap insects.
Sap Drinking
Hummingbirds have been observed drinking sap from wells made by sapsucker woodpeckers. The sap provides an additional energy source. Their specialized tongue allows them to efficiently lap up the sticky substance.
Filter Feeding
Some hummingbirds have been documented feeding by skimming tiny insect eggs and larvae from the surface of lakes. They will submerge their beak and use the water’s surface tension to draw water into their mouth, filtering out food particles.
Role in Pollination
The adaptations that allow efficient nectar feeding also make hummingbirds important pollinators. As they move between flowers, pollen attaches to their head and throat. When they visit the next blossom, some pollen rubs off to pollinate the plant.
Plants coevolved with hummingbird pollinators and developed flowers suited to their anatomy. Tubular blossoms perfectly match the hummingbird’s bill and tongue. The colors and chemistry of the nectar also attract hummingbirds.
By feeding on nectar, hummingbirds play a key ecological role. Their hollow tongue provides energy for the birds while enabling plant reproduction through pollination.
Conclusion
The unique anatomy of the hummingbird tongue enables specialized nectar feeding. The tongue contains branched filaments along the edges to collect nectar. Inside are hollow tubes that passively move nectar by capillary action without expending energy.
This efficient fluid transport would not be possible without the tongue’s hollow structure. Compression of the tubes as the tongue retracts allows hummingbirds to feed at rapid repetition rates. Together with other adaptations like tongue protraction, this provides hummingbirds exclusive access to certain flower types.
While the nectar diet is aided by the hollow tongue tubes, hummingbirds supplement with other foods like insects. Their versatile feeding methods provide the high energy needs of their fast-paced lifestyle. The coevolution of hummingbird tongue structure and tubular blossoms also makes them essential pollinators for many plant species.
