The Anhinga is a water bird often recognized by the common names “snake bird,” “darter,” or “water turkey.” This nickname comes from the bird’s habit of swimming with its body submerged, leaving only its long, slender neck and head visible above the water line, resembling a snake. The Anhinga is a highly specialized aquatic predator.
Identification and Geographic Range
The Anhinga is a large water bird, measuring approximately 34 to 36 inches (86 to 91 centimeters) in length with a wingspan of almost four feet. It possesses a notably long, sharply pointed, dagger-like bill, which distinguishes it from the hooked bill of the similar-looking cormorant. Its tail is long and fan-shaped, which is particularly noticeable when the bird is soaring high in the sky.
The plumage exhibits sexual dimorphism. Males are primarily glossy greenish-black, accented by silver-gray feathers on the upper back and wings that feature long, white plumes. Females have a lighter appearance, characterized by a brownish head and neck that contrasts with their darker body plumage.
This species inhabits warm, shallow waters across the Americas. The American Anhinga is found throughout the tropical and subtropical regions, ranging from the southeastern United States—specifically from North Carolina to Texas—southward through Mexico and Central America, and into South America, east of the Andes. Its preferred habitat includes freshwater lakes, slow-moving rivers, marshes, and cypress swamps, where it can easily find perches near the water.
Why They Swim Low: The Unique Feather Adaptation
The Anhinga’s ability to swim with its body completely underwater is a direct result of a specialized feather structure that lacks the waterproofing found in most other aquatic birds. Unlike most aquatic birds, the Anhinga’s feathers become easily saturated upon immersion. This feature allows water to collect within tiny spaces in the plumage, which eliminates the insulating air layer.
The resulting waterlogged plumage and the bird’s relatively dense bones reduce its buoyancy, enabling it to sink effortlessly and remain submerged. This lack of flotation is an adaptation that serves a specific purpose in its hunting strategy. It allows the bird to stalk fish slowly and silently underwater without the need to constantly fight against the natural upward force of the water.
Because their feathers become soaked, Anhingas cannot take flight for any extended distance immediately after a dive. They must exit the water and engage in a characteristic behavior of perching with their wings spread wide open to dry in the sun. This posture is a necessary step before they can fly efficiently again.
Hunting Strategy and Diet
The Anhinga is an ambush predator that uses its low-buoyancy swimming style to hunt effectively in the water. Instead of actively pursuing fish with speed, it swims slowly or hangs motionless just below the surface, stalking its prey among submerged vegetation. The diet consists primarily of small to medium-sized fish, although it will also consume crustaceans, amphibians, and aquatic insects.
The hunting technique involves a rapid, forceful thrust using its specialized neck structure, which contains a hinge-like apparatus. This anatomical feature allows the neck to be quickly extended like a spear. The bird then impales the fish with its long, pointed bill, often stabbing the fish through the sides with both mandibles.
After spearing a fish, the Anhinga surfaces to consume its catch. It typically tosses the impaled prey into the air and then catches it again to swallow it headfirst. The sharp, inward-pointing serrations inside the bill help to secure the slippery fish before it is tossed.