Hummingbirds are known for their ability to hover in midair and lick nectar from flowers with their long, forked tongues. But why did hummingbirds evolve to have split tongues in the first place? In this article, we’ll explore the unique anatomy of hummingbird tongues and how they allow hummingbirds to efficiently feed on nectar.
The forked tongue of hummingbirds
A hummingbird’s tongue is quite different from human tongues. Hummingbird tongues are long and forked, with two tubular tips. The length allows the tongue to reach deep into tubular flowers. The forked tips allow the tongue to lick nectar more efficiently.
When a hummingbird inserts its tongue into a flower, the forks anchor the tongue on the nectary. The nectary is the part of the flower that secretes sugary nectar. By anchoring its tongue on the nectary, the hummingbird can efficiently lap up the nectar.
The forks are also able to change position. This allows hummingbirds to altered how they are holding onto the nectary as they feed. The split structure means each fork can move independently, maximizing nectar uptake.
How hummingbird tongues evolved
Hummingbirds evolved from plain-tailed swifts, relatives of today’s swifts and swallows. The earliest hummingbirds had basic tubular tongues, similar to other nectar-feeding birds. Over time, their tongues evolved to have deeper grooves, and eventually split tips.
This tongue structure emerged as hummingbirds specialized in feeding on different flower shapes. Some flowers are deep, with hidden nectaries that require long, forked tongues to reach. Other flowers have wide openings that need broad tongued for efficient nectar uptake. Hummingbird tongues evolved to match the flowers they feed on.
In particular, the split tips provide more surface area for lapping up nectar. This allows faster feeding so hummingbirds can meet their high metabolism. Hummingbirds have the highest metabolism of all birds, so they need to feed almost constantly.
How the forked tongue works
Hummingbirds use capillary action to draw nectar into their forked tongues. When the bird places its tongue on a nectary, the nectar adheres to the grooves on the tongue surface. Adhesion and cohesion (molecular attraction) draw the nectar into the tubes of the tongue.
Pumping movements by the tongue and beak create suction that pulls more nectar onto the tongue. Some experts estimate that hummingbirds can lick 10-15 times per second as they feed.
The forked tips provide a larger surface area on the tongue for nectar collection. More nectar can adhere to the tongue, allowing each lick to extract the maximum amount of sweet fuel.
Hummingbirds also have hairy fringes on their tongue tips. These may help draw in nectar through capillarity. The fringe structure maximizes exposure to the nectar to uptake more per lick.
Other adaptations related to the tongue
Hummingbirds have several other adaptations that complement their unique tongue structure:
- A slender, curved bill that can easily fit into different flower shapes
- A groove in the upper mandible that the tongue can rest in when retracted
- Salivary glands that quickly secrete liquid to dissolve the sugar in nectar
- An enlarged liver that efficiently processes the sugar in the nectar
All these specializations allow hummingbirds to rapidly and efficiently feed using their forked tongues. The slender bill reaches the nectar, the tongue laps it up, and the digestive system quickly metabolizes it for energy.
Differences between hummingbird tongues and other bird tongues
Most other bird species do not have forked tongues. However, some other nectar-feeding birds like sunbirds and honeyeaters also have adaptations like brush-tipped tongues that allow them to uptake nectar.
Insect-eating birds like flycatchers have short, pointed tongues to snare insects. Seed-eating finches have thicker, more rounded tongues that help manipulate seeds.
So while forked tongues are uniquely adapted to nectar-feeding, variations in tongue structure match different feeding strategies across birds. Hummingbird tongues stand out as being extremely long and doubly forked for specialized nectar extraction.
Oddities of the hummingbird tongue
Beyond being forked, hummingbird tongues have some other unusual features:
- Their tongues have no taste buds. Hummingbirds don’t taste the nectar they drink.
- Their tongues function as a micropump, with ability to suck nectar even when the head is higher than the food source.
- They can retract their tongues into a sheath-like groove in their upper beak when not feeding.
- Their tongues are so long that they wrap around their skulls when retracted.
These oddities illustrate just how highly specialized hummingbird tongues are for nectar feeding. Form and function are precisely streamlined by evolution.
Disadvantages of the forked tongue
The forked hummingbird tongue does have some drawbacks:
- It is less efficient at catching insects, so hummingbirds rely more heavily on nectar for nutrition.
- Pumping the tongue in and out requires a lot of energy. Hummingbirds compensate by having rapid metabolism.
- Species with longer forked tongues are more prone to starving when flower nectar is less available.
However, the advantages of the hummingbird’s tongue structure outweigh these costs. Access to rapid energy from nectar far outweighs the energy needed to pump the tongue. This is especially true since hummingbirds adapted a rapid metabolism and small body size.
Conclusion
In summary, hummingbirds evolved forked tongues in order to specialize in feeding on floral nectar. The long, split tongue provides an ideal structure for lapping up nectar quickly and efficiently. This matches the high metabolism of hummingbirds that requires a constant energy source. NEXT, we’ll explore how the tongue allows hummingbirds to access a wide variety of different flower shapes and sizes.
How the forked tongue allows access to different flowers
Hummingbirds have an ingenious feeding method – they can feed from flowers of many different shapes thanks to their forked tongues. Here’s how the tongue allows access to so many flowering plants:
- Two thin tubes (the forks) can probe deep into tubular and curved flowers that have hidden or deeply placed nectaries.
- Forks allow nectar extraction from flowers with wide openings by providing a larger surface area for licking.
- Their tongue tips are slightly fringed to maximize nectar exposure.
- The forks can move independently and reposition while feeding to optimize nectar uptake.
In addition, hummingbirds have slender, slightly curved beaks adapted to different flower shapes. So it’s the pair of a dexterous forked tongue and specialized beak that allows hummingbirds to access such a diversity of flowers.
Feeding from tubular flowers
Many hummingbird-pollinated flowers have a tubular shape. Examples include trumpet vine, cardinal flower, and salvia. The nectar at the base of these flowers can be an inch or more down inside the curved tube.
Hummingbird tongues are able to probe down into even very long and slender tubular flowers. When inserted into the tube, the forked tips ensure contact with the nectary to adhere to the maximum amount of nectar.
Feeding from open flowers
Some hummingbird-visited flowers like columbine and fuchsia have an open shape. While the nectar is more exposed, it still takes energy to extract it. The forked tongue covers more surface area on these open flowers to collect nectar efficiently.
The forks can flex and position to coat themselves in nectar. The hummingbird then simply curls the nectar-coated tongue back into its mouth to feed.
Specialized bill shape
Hummingbird beaks match their split tongues by being slim, tapered, and slightly curved. This shape allows easy access to different flower shapes. The curvature and angle of the beak complements that of the tongue for efficient feeding.
Similar to needle-nose pliers, the bill can precisely hold and position flowers to allow the tongue to reach the nectar. The streamlined beak doesn’t slow down the rapid Actions of the tongue.
Differences in tongue feeding among hummingbird species
There are over 300 hummingbird species, and they have adapted tongues optimized for the flowers in their preferred habitats.
Hermit hummingbirds, who feed on long tubular flowers, have the longest tongues relative to their size. Patagona or Giant hummingbirds have the longest tongues overall, to match their larger size and the giant flowers they pollinate.
Some hummingbirds like bee hummingbirds have shorter, wider tongues ideal for feeding on short, wider flowers.
Mango-feeding hummingbirds have curved bills and tongues allowing them to take nectar from flowers with a punch cone shape. Hook-billed hermits also have specialized beak and tongue sets to their unique food plants.
So while having a forked tongue is universal, different species have adapted tongue length, curve, and fork spread to their particular flower sets.
An evolutionary race
The evolution between hummingbird tongues and flower shapes reflects a classic coevolutionary race. Flowers adapt deeper tubes to try to prevent nectar theft from insects. Hummingbirds, in turn, evolve longer tongues and beaks in order to access this hidden treasure.
New hummingbird species emerge, with altered tongue shapes that allow them to gain a competitive edge by feeding from flowers untouched by other birds. It’s a never-ending race of adaptation.
Do other pollinators have forked tongues?
Hummingbirds are not the only pollinators with forked tongues adapted for feeding on nectar. Some other examples include:
- Butterflies – Species like the pipevine swallowtail have split tongues with a central tube and two lateral tubes.
- Honeyeaters – These related to hummingbirds have forked bristle-tipped tongues.
- Sunbirds – Another relative of hummingbirds that shares their long forked tongues.
- Bats – Nectar-feeding bats tend to have long tongues often split at the tip.
However, hummingbirds take tongue specialization to another level. Their tongues have uniquely elongated lengths to match tubular flowers. Fringe structures and curved beaks also maximize nectar uptake.
Hummingbirds can feed faster, on more flower shapes, than any other nectar feeder. They owe this competitive edge to tongue and beak adaptations evolved over millenia.
Conclusion
A hummingbird’s forked tongue provides an optimal design for feeding on floral nectar. The split structure offers a larger surface area, flexibility, and ability to probe deep into different flowers. Complemented by a slim, curved bill, the tongue can access a wide range of blossoms.
Differences in tongue structure among species matches the varied flower shapes in each hummingbird’s habitat. This evolutionary adaptation gave hummingbirds a competitive edge, allowing them to exploit nectar sources unavailable to other pollinators.
While less pronounced, some other nectar feeders like butterflies and honeyeaters also show tongue forking. But hummingbirds have refined split tongues to an unparalleled degree that supports their demanding metabolism.
The next time you see a hummingbird lick nectar with its elegant forked tongue, appreciate the exquisite evolution that shaped this micropump for feeding.
