Lorikeets are a group of small to medium sized parrots that are characterized by their bright plumage and specialized brush-tipped tongues. There are over 50 species of lorikeet that are found throughout Australia, New Guinea, and various islands in the Pacific. The unique structure of the lorikeet tongue allows them to feed primarily on nectar and pollen.
What makes the lorikeet tongue unique?
The most distinctive feature of the lorikeet tongue is that it is covered in tiny hair-like structures called papillae. These papillae act like a brush or mop to help lorikeets soak up and ingest nectar. Under a microscope, the lorikeet tongue appears hairy or shaggy due to the dense layer of papillae coating the surface.
The papillae on a lorikeet’s tongue have a few specializations that make them highly effective nectar gathering tools:
- The papillae act like tiny tubes or capillaries to draw nectar into the mouth. They essentially soak up the nectar and then the tongue retracts to squeeze the nectar back to be swallowed.
- The tips of the papillae secretes substances that causes pollen grains to stick. As the bird probes flowers, pollen sticks to its tongue and allows the lorikeet to transfer pollen between flowers.
- The tongue is also slender and can be extended far outside the beak allowing the bird to probe even the deepest flowers.
Additionally, lorikeets have a larger tongue with more surface area compared to other parrots of the same size. Having more papillae packed into this larger tongue gives it a higher nectar holding and gathering capacity.
What does the surface of the tongue look like?
When viewed under an electron microscope, the surface of a lorikeet’s tongue appears dense and fuzzy due to the carpet of papillae. The papillae are organized into even rows and columns, almost like bristles on a brush. They are slender, hair-like structures typically 0.3-0.5mm long.
There can be anywhere from 35 to 150 papillae per square millimeter on different parts of the tongue. The tips are often described as “swollen” or club-shaped compared to the narrower bases of the papillae. This club-like shape likely helps with scooping and holding nectar.
Interestingly, the tongue surface is not uniformly covered with papillae. The tip of the tongue where nectar is loaded is usually the most densely covered in papillae. Further back towards the throat, there are fewer papillae, sometimes interspersed with thick conical protrusions called lingual protuberances.
In cross-section, papillae are narrow hollow tubesAround 300 micrometers long and 20 micrometers wide. This tubular shape allows nectar to move through capillary action from the tip to the base of each papilla.
Comparison to other bird tongues
The lorikeet tongue stands in stark contrast to the tongues of seed eating parrots. Parrots like budgerigars or cockatiels have a tongue without papillae. Instead, their tongue is smooth with just a slight indentation in the center.
Hummingbirds, another major nectar feeder, also have tongues covered in hair-like papillae. However, hummingbird papillae tend to be fewer in number and arranged differently than lorikeet tongues. Papillae on hummingbird tongues are forked or branched, while lorikeet papillae are simple tubes.
These differences highlight how specialized the lorikeet tongue is for gathering nectar.
Bird Group | Example Species | Tongue Structure |
---|---|---|
Lorikeets | Rainbow lorikeet | Densely packed simple papillae |
Seed-eating parrots | Budgerigar | Smooth tongue surface |
Hummingbirds | Ruby-throated hummingbird | Sparse branched papillae |
Functions of the lorikeet tongue
The specialized tongue of lorikeets allows them to exploit flower nectar as a food source. Here are some of the key functions the tongue performs:
- Nectar collection – The papillae act like tiny hollow tubes that use capillary action to soak up and collect nectar. Having more densely packed papillae increases nectar gathering efficiency.
- Pollen transfer – Pollen sticks to secretions on the tongue tip and is transferred between flowers as the bird feeds. This facilitates pollination between plant species that rely on lorikeets.
- Flower probing – The slender, extendible tongue can probe even the deepest tubular flowers like eucalyptus blossoms.
- Water reach – Lorikeets can use their specialized tongue to drink or reach water that is otherwise unreachable at the bottom of long, narrow openings.
Lorikeet tongue adaptations
Several evolutionary adaptations make the lorikeet tongue so highly specialized for nectar feeding:
- Smaller tongue with more densely packed papillae compared to body size
- Thinner, more numerous papillae provide more surface area
- Club-shaped papillae tips for trapping liquid
- Hollow, tubular papillae to harness capillary action
- Ability to protract tongue outside the beak for flower probing
- Roughened tongue tip to help pollen adhesion
- Thick saliva resistant to abrasion from sugar-rich nectar
These adaptations allow lorikeets to exploit food resources that are inaccessible to other birds. Feeding on nectar provided an ecological niche that lorikeets could occupy and diversify into.
Role in feeding
The unique structure of the tongue is perfectly suited for gathering nectar from flowers. Here is how lorikeets use their tongue when feeding:
- The lorikeet hovers up to a flower and inserts its specialized tongue deep into the corolla while holding onto the rim with its beak.
- The papillae on the tongue tip soak up and collect nectar through capillary action.
- Secretions cause pollen grains to stick to the tongue tip.
- The bird then retracts its nectar-covered tongue back into its mouth.
- Powerful tongue muscles squeeze the tongue to pump nectar to the back of the throat to be swallowed.
- Pollen is transferred between flowers as the bird feeds and leads to pollination.
This feeding method means lorikeets don’t need to land on flowers to feed. They can extract nectar while hovering which likely makes them more efficient nectar feeders.
Threats and injuries
The unique adaptation of the lorikeet tongue comes with some risks and vulnerabilities as well. Some potential threats and injuries include:
- Abrasion – Constant exposure to sugary nectar can lead to splits or ulcers on the tongue surface.
- Entrapment – Tongues can become caught or trapped inside deep tubular flowers.
- Bites – Injuries from biting their highly sensitive tongue on food.
- Dehydration – Relying solely on nectar puts lorikeets at risk of dehydration.
- Defense – Having a large protruding tongue makes it a target for predators.
Fortunately, the constant regeneration of papillae cells on the tongue surface helps heal any minor injuries. But major damage to the tongue can place lorikeets at risk of starvation and infection.
Conclusion
The unique, brush-like tongue of lorikeets plays an integral role in their survival. It allows them to exploit an abundant but difficult to access food source in the form of flower nectar. Dense rows of hair-like papillae use capillary forces to soak up and collect nectar with incredible efficiency. While the tongue confers many benefits, it also leaves lorikeets vulnerable to certain threats and injuries. This highlights the tradeoffs and risks associated with such a highly specialized foraging adaptation.