Ornithologists have recorded the presence of more than six hundred bird species within the Tambopata National Reserve in southeastern Peru. One of the species of birds most often seen by visitors to this biodiversity hotspot is the snakebird (Anhinga anhinga).
Its English name is a direct translation of the name Anhinga, given to it by speakers of the indigenous Tupi language. The name is derived from the characteristic S-shape of the bird’s long neck. When the snakebird swims, often only its neck and head are visible above the water, so that it resembles a snake preparing to strike.
Snakebirds are only found in the lowland tropical and subtropical forests of South America, and on the Caribbean islands of Trinidad and Tobago, although they are known to be closely related to Indian, African and Australian species of darter (another name for the snakebird is the American darter). Only those populations that occupy the far north and south of the snakebird’s range are known to migrate. Migratory snakebirds have been spotted as far north as Wisconsin, in the United States.
In common with the other species of darters found on different continents, the snakebird feeds by spearing fish and occasionally other prey with its long beak. Snakebirds do not have waterproof feathers, and their plumage becomes soaked when hunting. After swimming with its body either completely or partially submerged, typically the snakebird will dry out its plumage by perching on logs or low branches, with its wings stretched out and its tail spread. This is how snakebirds are often spotted along riverbanks or lakeshores within the forests of the Amazon basin.
Because of their similar behavior and similar size and profile, when birdwatching at a distance it is easy to mistake double-crested cormorants for snakebirds; however, the tail of the snakebird is much longer and more fan-like than that of the cormorant.
Male adult snakebirds have a glossy greenish black body, while their wings and tail are a bluish black. They have silver or white streaks on their back and wingtips. Females and juveniles have pale tan-colored or grayish coloring on the head, neck and breast. Adult snakebirds are large, with a body length of up to 95 centimeters (37 inches) and a wingspan of up to 103 centimeters (43 inches). The bill, legs and feet are yellow. Used for spearing prey, the bill is about twice the length of the head, ending in a sharp point. Hatchlings emerge bald, before gaining tan feathers after a few days. Their plumage will then change to white, before acquiring the overall tan color seen in juveniles.
Snakebirds are aquatic. They swim underwater using their webbed feet, stretching out their long necks to spear their prey with their beak. The snakebird feeds mostly on medium-sized fish. Once it has speared its prey it will bring it to the surface before swallowing it head first. Across their range, snakebirds are also known to feed on crabs, crayfish and aquatic insects.
While the snakebird is unable to fly with wet feathers, once it has dried out it will often soar high into the air, sailing on thermals with little apparent effort, far above the rivers and forests of its preferred habitat. Its long beak and neck give the snakebird a cross-like appearance when in flight.