Anhinga

Meet the Anhinga: The Snakebird of North American Waters

Often called the “snakebird” due to its sinuous swimming style, the Anhinga is a fascinating waterbird found in the warm, slow‑moving waters of the southeastern United States and across Central and South America. Its unique hunting technique and distinctive appearance set it apart in the avian world. This guide explores the life history, behavior, and ecological role of this remarkable creature.

Identification and Physical Characteristics

The Anhinga is a large bird, measuring approximately 27 to 37 inches in length with a wingspan of 45 to 58 inches. Males are easily distinguished by their glossy black plumage, accented by a silvery‑white band across the back and wings. The males also exhibit a striking iridescent greenish‑blue patch on the throat during breeding season. Females, while similar in shape, are browner overall with a more subdued coloration. Both sexes possess a long, slender neck and a dagger‑like bill perfectly adapted for spearing fish. Notably, the Anhinga’s plumage is not fully waterproof, a key adaptation for its underwater hunting strategy.

Habitat and Distribution

Anhingas thrive in a variety of aquatic habitats including freshwater lakes, swamps, marshes, canals, and slow‑moving rivers. They prefer areas with abundant vegetation and fish populations. In the United States, their range extends from the Carolinas west to Texas and north into the Mississippi Valley. They are year‑round residents in Florida and along the Gulf Coast. The Anhinga also boasts a widespread distribution throughout Central and South America, from Mexico to Argentina.

Diet and Hunting Techniques

The Anhinga is primarily a piscivore, meaning its diet consists almost entirely of fish. They are skilled hunters, employing a unique and captivating technique. Anhingas submerge themselves completely, leaving only their eyes and nostrils above the water’s surface. They then spear fish with their sharp, pointed bills. Once caught, the fish is tossed into the air and swallowed headfirst. This technique is so effective that Anhingas have earned the nickname “snakebird” due to their snake‑like appearance while swimming. They also consume crustaceans, amphibians, and occasionally small reptiles.

Behavior and Social Structure

Outside of breeding season, Anhingas are often seen in small groups, foraging and roosting together. They are known for spreading their wings after swimming, allowing the sun to dry their plumage. This behavior is not solely for drying; it also helps with thermoregulation. They are relatively quiet birds, but can emit a variety of croaking and hissing sounds, especially during courtship or when disturbed.

Reproduction and Life Cycle

Anhingas are colonial nesters, often building their nests in groups within trees or shrubs overhanging water. Nests are constructed from sticks and lined with aquatic vegetation. The breeding season typically occurs from spring to summer. The female lays 4 to 6 pale blue eggs. Both parents incubate the eggs for approximately 25 to 30 days. Chicks are altricial, meaning they are born helpless and require extensive parental care. Young Anhingas fledge, or leave the nest, at around 6 to 7 weeks of age, but continue to rely on their parents for food for several weeks afterward.

Ecological Role and Interactions

Anhingas play an important role in aquatic ecosystems as predators of fish. They help regulate fish populations and contribute to the overall health of the ecosystem. They are also prey for larger birds of prey, such as hawks and owls, and mammals, like raccoons and foxes. Anhingas often forage alongside other waterbirds, such as herons and egrets, creating a diverse and dynamic community. They sometimes compete with other piscivorous birds for resources.

Anhinga and Human Interactions

Historically, Anhingas were hunted for their feathers, which were used in decorative items. However, this practice has largely ceased. Today, Anhingas are more likely to be observed and appreciated by birdwatchers and nature enthusiasts. Habitat loss and water pollution remain the primary threats to Anhinga populations. Conservation efforts focused on protecting and restoring wetlands are crucial for ensuring the long‑term survival of this fascinating species.

Interesting Facts About Anhingas

• Anhingas can completely submerge themselves for up to 20 minutes.
• Their skeletal structure is highly pneumatic, meaning their bones are filled with air sacs, which aids in buoyancy.
• Male Anhingas often display their wings during courtship to attract females.
• Anhingas are capable of flying long distances in search of food and suitable nesting sites.
• They are surprisingly agile on land, despite their awkward appearance.

For the Aspiring Zoologist: Anhinga Evolution and Taxonomy

The Anhinga belongs to the family Anhingidae, a small family containing only four species worldwide. Fossil evidence suggests that the family has a long evolutionary history, dating back to the Eocene epoch. The Anhinga is closely related to the other three species—the Oriental Anhinga, the African Darter, and the Brazilian Darter. Phylogenetic studies based on molecular data have helped clarify the evolutionary relationships within the family.

For the Zookeeper: Anhinga Care in Captivity

Caring for Anhingas in captivity requires a specialized approach. They need a large aviary with a sizable pool of water deep enough for them to submerge and swim. The pool should be regularly cleaned to maintain water quality. Their diet should consist primarily of live fish, supplemented with vitamins and minerals. Providing opportunities for them to exhibit natural behaviors, such as diving, swimming, and drying their plumage, is crucial for their well‑being. It’s important to avoid providing perches that are too high, as they are not strong fliers over long distances.

Encountering an Anhinga in the Wild: A Hiker’s Guide

If you encounter an Anhinga while hiking near water, observe it from a distance. Avoid disturbing its natural behavior. Do not approach the bird or attempt to feed it. If you notice an injured or distressed Anhinga, contact your local wildlife rehabilitation center for assistance.

Conclusion

The Anhinga is a captivating and unique waterbird that embodies the beauty and complexity of the natural world. Its remarkable hunting techniques, distinctive appearance, and ecological role make it a valuable and fascinating species to study and appreciate. By understanding and protecting their habitat, we can ensure that these magnificent birds continue to thrive for generations to come.