The anhinga is found in warmer regions of the Americas. Being members of the family of darters, they are related to cormorants and pelicans. "Anhinga" come from the Tupi language of Brazil and means snake bird or devil bird. These Central and North American birds are skilful swimmers with unique characteristics that help them when hunting for fish. With a large wing span, they are able to fly in the manner of a vulture or a hawk. Males and females look different, with the females being smaller and browner and the males blacker. Their feathers provide less buoyancy than ducks, so they are able to dive under the water, and swim with just their thin necks above the water, earning them the nickname of the "snake bird".
Anhingas live all year round in southwest coastal areas of the United States, from North Carolina to Texas. They are also found in Central America, Mexico, Panama, and Cuba, and in South America from Colombia to Ecuador, and in the east of the Andes to Argentina. Anhingas live in tropical and subtropical areas. They prefer waters that are fresh or brackish, and can sometimes be found on coasts. They live near lakes, marshes, and mangrove swamps with tall trees and thick vegetation, and in shallow lagoons and bays.
Anhingas are diurnal and generally solitary but may gather with cormorants, herons, ibises, and storks. They will nest with their species and other birds in loose colonies but do not associate with other anhingas aside from in nesting colonies. These birds are highly territorial, engaging in exaggerated displays when defending their nest site: spreading their wings and snapping their beak to threaten an intruder, leading to a fight if necessary, pecking each other on the neck and head. When they are in the water they spend most of their time fishing, otherwise, they will be found perched in trees. They often crawl out of the water to find a high perch so they can sun themselves. As with turkey vultures and cormorants, anhingas will spread out their wings to sun themselves, which dries out their plumage, absorbing heat from the sun. They lose heat quickly in water as they have no layer of body feathers to provide insulation, thus, the sun's heat helps them to maintain their body temperature.
Anhingas are monogamous, forming strong pair bonds, which last for life. During courtship, anhingas perform flying displays, soaring towards their nest from a great height. Birds in Mexico perform a particular display when they are at the nest, vocalizing to each other, stretching their neck towards their mate. Breeding is seasonal in North America. In latitudes that are subtropical or tropical, breeding can be throughout the year, or triggered by dry or wet seasons. Anhingas usually nest in colonies, sometimes with other bird species. The nest is built by both adults and is used then from year to year. 2 to 5 eggs are laid and incubation is for around 25 to 30 days, done by both parents. Chicks are naked and helpless when they hatch and may have some dark and white down along their sides. They are brooded for 12 days by both parents and remain in their nest for three weeks. Then they climb out of their nest onto a branch, and they fledge at about 6 weeks old. The young stay for several more weeks with their parents before becoming independent and reach maturity when they are about 2 years old.
In the Americas, this species is abundant, despite their aquatic habitats being threatened. DDT (poison) has had an effect on their reproductive success, and banning this pesticide in the United States has benefited those populations that breed in the south of the country.
According to All About Birds resource, the total breeding population of the anhinga is 83,000 individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but their numbers today are decreasing.