Hummingbirds are famous for their incredibly long tongues which allows them to reach deep into flowers to extract nectar. But why did hummingbirds evolve to have such elongated tongues in the first place? Here we’ll explore the evolutionary advantages and fascinating adaptations that make the hummingbird’s tongue so unique in the animal kingdom.
The Importance of Nectar for Hummingbirds
Hummingbirds are nectarivores, meaning their diet consists almost entirely of plant nectar. Nectar provides hummingbirds with the high-energy carbohydrates they need to support their hyperactive lifestyle. The average hummingbird has a heart rate over 500 beats per minute and flaps its wings up to 80 times per second during hovering flight. This generates huge energetic demands for a bird weighing only 2-20 grams. Just to survive, hummingbirds need to consume more than their own body weight in nectar each day.
Given their extreme dependence on nectar, it’s not surprising that evolutionary pressures led hummingbirds to develop highly specialized adaptations for gathering this precious resource efficiently. An elongated tongue is one such key adaptation.
Why Hummingbirds Need Long Tongues
Many flowers have evolved deep, tubular shapes perfect for accessing nectar via a long thin beak or tongue. Native bee species often have tongues ranging from 5-6 mm in length. But a hummingbird’s tongue is far longer proportional to its body size. The average hummingbird tongue measures around 4 cm (over 1.5 inches). Here are some key reasons why the hummingbird tongue needed to become so elongated:
- To reach nectar at the base of long tubular flowers
- To lap up more nectar with each lick
- To outcompete other nectar feeders like bees and butterflies
- To efficiently feed while hovering without landing on flowers
Next we’ll look at the unique anatomical adaptations that allow hummingbirds to sport such impressively long and flexible tongues.
Anatomical Adaptations
A hummingbird’s tongue consists of two tubes that zip together to form a long, forked strand. This unique anatomical arrangement offers several key benefits:
Extensibility
The two tubes can slide in and out past each other, allowing the tongue to extend far beyond its resting length. Some parts of the tubes are bound by elastic ligaments that snap the tubes back into a contracted position when retracted into the beak.
Flexibility
Since it’s split down the middle, the tongue can bend and flex to carefully probe flowers and lap up nectar. Studies show hummingbird tongues are so flexible they can bend 180 degrees.
Protrusibility
Hummingbirds have modified hyoid bones in their throat that act like a piston, allowing them to rapidly shoot their tongues in and out with great force. Their tongue can dart up to around 20 times per second when feeding.
Nectar Manipulation
The forked tip of the tongue has fringed edges that help collect and hold liquid nectar through capillary action. And grooves on the top surface of the tongue channel nectar toward the back of the mouth when the tongue retracts.
| Anatomical Adaptation | Benefit |
|---|---|
| Extensibility | Allows tongue to extend longer than its resting length |
| Flexibility | Enables tongue to bend to probe flowers |
| Protrusibility | Allows rapid darting of tongue in and out |
| Fringed forked tip | Helps collect and hold liquid nectar |
| Nectar grooves | Channels nectar toward throat when tongue retracts |
Together these adaptations allow hummingbirds to drink efficiently from flowers not accessible to many other pollinators.
Feeding Strategies and Behaviors
Of course, it’s not enough to just have a long tongue – hummingbirds have had to evolve specialized feeding strategies to take advantage of their unique anatomy. Here are some of the key ways hummingbirds use their elongated tongues while feeding on nectar:
Hover Feeding
Hummingbirds can precisely maintain a hovering position in front of a flower while extending their tongue into the corolla of the flower. This allows them to drink without having to land and perch on the flower.
Lapping
Hummingbirds use their tongues like a tiny paintbrush, extending it rapidly in and out to lap up nectar. This lapping behavior can occur up to 20 times per second!
Pumping
At longer tubular flowers, hummingbirds will insert their entire bill into the corolla and pump their tongue in and out. This pumps the flower’s nectar into their mouth.
Wiggling and Curling
Hummingbirds will twist and curl their tongue while probing inside flowers, allowing them to exploit the last drops of nectar within crevices.
Side-Feeding
Hummingbirds can flex their neck to feed from the side or even upside-down on flowers, aided by their specialized tongue.
Role of Tongue Length in Hummingbird Evolution
The key evolutionary innovations of elongated tongue paired with efficient hover-feeding opened up a new ecological niche for hummingbirds. Access to nectar-rich tubular flowers not effectively pollinated by insect species provided hummingbirds with an abundant food source. This drove both co-evolution of specialized flowers in symbiosis with hummingbirds and further adaptation of hummingbird anatomy over time.
There is evidence that tongue length played a key role in enabling different hummingbird species to adapt to specialized feeding niches:
- Species with the longest tongues feed on flowers with the deepest corollas.
- Broad-tailed hummingbirds have the shortest tongues and feed primarily on more open flowers.
- Bee and hermit hummingbirds have intermediate tongue length suited for shorter tubed flowers.
Differences in tongue length likely minimized interspecies competition among hummingbirds flowering in the same ecosystem. This enhanced the community diversity of hummingbirds across the Americas.
| Hummingbird Species | Average Tongue Length | Preferred Flowers |
|---|---|---|
| Blue-throated Hummingbird | Over 5 cm | Long tubular flowers |
| Broad-tailed Hummingbird | Around 2.5 cm | Open flowers |
| Anna’s Hummingbird | 3-4 cm | Short-moderate tubed flowers |
Conclusion
A hummingbird’s elongated tongue is an elegant evolutionary solution enabling effective nectar feeding. The tongue’s specialized anatomy allows hummingbirds to exploit flower shapes unavailable to most other pollinators. This provided hummingbirds exclusive access to an abundant high-energy food source. In turn, specialized flowers evolved to attract pollination by hummingbirds. The co-evolution of hummingbirds and plants shaped the community diversity we see today across American ecosystems.
