Anhingas are a fascinating species of water bird that are known for their habit of spreading their wings open to bask in the sun. This unusual behavior serves several important purposes for the anhinga. In this article, we’ll explore the reasons why anhingas assume this iconic wing-spreading posture.
Thermoregulation
One of the main reasons anhingas spread their wings is to help regulate their body temperature. Anhingas do not have waterproof feathers like ducks and other waterfowl. This allows them to dive and swim underwater easily when hunting for fish. However, it also means they can get waterlogged and chilled when floating on the surface.
By holding their wings open, anhingas allow the sun to warm and dry their feathers. The sun’s heat replaces body heat lost during swimming and dries the feathers so the anhinga can regain buoyancy and insulation. Wing-spreading behavior is very common after anhingas emerge from a swim in order to raise their core temperature back up.
Staying Warm in Cold Water
Anhingas thrive in warmer climates and are found near freshwater lakes, rivers, and swamps in tropical and subtropical regions. However, some species can migrate to temperate zones for breeding. The waters in these cooler regions can cause them to lose heat rapidly.
By basking in the sun with outstretched wings, anhingas can raise their temperatures high enough to endure swimming and diving in chilly water. Their wings help collect solar radiation and prevent conductive heat loss across their body surface area.
Feather Drying
In addition to warming their bodies, anhingas also spread their wings to speed up feather drying. As mentioned earlier, anhinga feathers get soaked during swims because they are not water-repellent like a duck’s.
It takes time for water to evaporate off anhinga feathers. Holding their wings open allows air circulation to dry the plumage faster. It also maximizes the feather surface area exposed to the drying effects of the sun’s heat.
Regaining Buoyancy
When anhinga feathers are waterlogged, it makes the birds less buoyant and more likely to sink. This is problematic when they need to float on the water’s surface while hunting and searching for fish.
By fanning their wings open to dry, anhingas can regain their natural buoyancy. Having drier, airier plumage allows them to float higher in the water and swim with less effort.
Preening Access
The wings-spread posture also gives anhingas easy access to preen and straighten their feathers after a swim. Preening is how birds clean and maintain their plumage by distributing waterproofing oils from a gland near the base of their tail.
With their long neck and bill, anhingas can neatly preen every contour of their wings and body while holding them outstretched. Directing sunlight also helps them see and re-align any feathers that got disheveled while diving underwater.
Oil Distribution
Due to their lack of waterproofing, anhinga feathers can get separated and clumped together when wet. The sunlight helps open and separate their feathers to allow preening oil to reach any damaged areas.
Spread wings may also enable better distribution of preen oil across all the feathers. Oil is transferred from the gland to the bill during preening and then applied to feathers.
Drying the Wings
Anhingas are unable to fly with wet wings. Their long wingspans of around 45 inches provide the lift they need to stay aloft.
After swimming, anhingas must first spread their entire wings to dry before taking flight. The large surface area absorbs heat from the sun and allows air currents to evaporate moisture trapped in the feathers.
Short Flight Distance
Wings that are not fully dried can cause an anhinga to have a hard time getting airborne. They may only be able to fly short distances until their wings dry out sufficiently.
By spreading their wings early, anhingas ensure they will be capable of making longer flights to reach feeding areas or avoid threats once they are ready to fly.
Visual Threat Display
Interestingly, the wings-spread posture of sunbathing anhingas also serves as a visual warning to potential predators. With a wingspan approaching four feet, the soaring silhouette of an anhinga is dramatic and intimidating.
By displaying their wings, anhingas signal that they are alert and aware of nearby threats. Their wings are also spread in preparation for quickly taking flight to escape an approaching predator.
Territorial Display
In addition to deterring predators, wing-spreading can also communicate territorial boundaries to other male anhingas. Males are very territorial and use posturing as threats during breeding disputes.
The size and appearance of spread wings indicates fitness, strength, and readiness to fight a rival male over nesting sites or mates.
Conclusion
Anhingas have fascinated biologists and birdwatchers with their unique soaking and wing-spreading behaviors. As we have discussed, holding their wings open to the sun provides several benefits:
- Thermoregulation to raise body heat after swimming
- Drying waterlogged feathers faster
- Better access for preening feathers
- Drying wings before flight
- Warning visual display to deter predators and rivals
The next time you see an anhinga stationed in shallow water with outstretched wings, you can appreciate the many purposes behind this solar posture. It is a great example of the specialized behaviors and adaptations that allow wetland birds to thrive in their environments.
| Benefit | Description |
|---|---|
| Thermoregulation | Absorbs heat from the sun to warm up after swimming |
| Feather drying | Exposure to sun and air dries waterlogged feathers faster |
| Preening access | Can reach all feathers easily to distribute preen oil |
| Wing drying | Ensures wings are dry enough for flight |
| Threat display | Spreads wings as a warning to predators and rivals |
Anhingas are fascinating water birds that have evolved some very unique behaviors and adaptations for their wetland lifestyle. Their iconic habit of spreading their wings to the sun serves a variety of important functions. The next time you spot an anhinga “sunbathing”, take a moment to appreciate the ingenuity behind this unusual behavior.
