The Anhinga is among the most distinctive of North American birds, with long, snakelike neck, straight bill, large fanlike tail resembling that of a turkey (Meleagris gallopavo; from which the former name Water Turkey was derived), corrugations on its central rectrices, and unique swimming, flight, and behavior patterns. This truly aquatic species spends its life in water or on branches overhanging protected, usually freshwater streams and ponds. Unlike most aquatic birds, Anhingas have fully wettable plumage and dense bones, adaptations that allow them to achieve neutral buoyancy in water, facilitating a slow, stalking hunting habit while submerged in shallow aquatic vegetation, where they spear fish. The neck vertebrae are arranged to allow a strong and rapid stab. While the bird is swimming on the surface, its body is usually submerged, with only the head and snakelike neck visible, making it obvious why the term “snake bird” is often applied. The word “Anhinga” is derived from a Tupi (Brazilian) Indian name, anhingá or anhangá, for the devil bird, an evil spirit of the woods (Jobling Jobling 1991). The wettable plumage of this species results in considerable loss of body heat underwater, with a concomitant need for large amounts of time spent sunning and drying feathers later. One habitat require-ment of this bird is the availability of logs and branches near the water onto which individuals can climb in order to sun. The strong dependence of this bird on sun warmth for thermoregulation limits its northern distribution. Anhingas are strong fliers, often soaring at great altitude above their wetland habitats with wings held flat and neck out, presenting a distinct cross. This species is social and nests colonially, often with long-legged wading birds. It builds its nests in trees overhanging water, and the young birds, which can swim long before they can fly, often escape by jumping into the water.
Some aspects of this species have been well studied. Musculature, molt, and adaptations for flight and swimming have been described in detail by Owre (Owre 1967a) and Casler (Casler 1973); comparative behavior by van Tets (Van Tets 1965); thermoregulation by Henneman (Hennemann III 1982, Hennemann III 1983, Hennemann III 1985); systematics by Siegel-Causey (Siegel-Causey 1988b, Siegel-Causey 1996, in press); and breeding behavior and ecology by Meanley (Meanley 1954), Owre (Owre 1967a), Allen (Allen 1961b), and Burger et al. (Burger et al. 1977a, Burger et al. 1978). Relatively little is known about social organization, demography, migration, or movements. Nearly all studies of this bird have been done in the United States; little is known about it in Central and South America.