Although anhingas resemble cormorants (Phalacrocorax species), the two have several differences. Cormorants are more powerful swimmers and thus able to hunt faster-swimming fish, whereas anhingas are much slower in the water and hunt slower-swimming fish. Anhingas are able to soar, but require gliding flights from trees in order to start flight, unlike cormorants, which are not able to soar and can easily take off from the water. Anhinga distributions are more limited by temperature due to their low metabolic rate. Cormorants are able to maintain higher body temperatures and are found in colder regions of North America. Also, anhingas use a flap and glide form of flight, whereas cormorants continually flap.
Normally quiet birds, vocalizations include clicks, rattles, croaks, and grunts. Anhingas typically call while on or near the nest, and occasionally while flying or perching. They are particularly silent and elusive when flightless due to molting.
Communication Channels: acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
In the Americas, anhingas are abundant, although their aquatic habitats are threatened. DDT was found to have an effect on the reproductive success of these birds and banning of this pesticide in North America has benefited those birds that breed in the southern United States.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
In North America, anhingas have no particular economic impact, particularly since they do not eat the fish that humans might.
Anhingas and their eggs are eaten by humans in parts of Asia.
Positive Impacts: food
Anhingas prey primarily on fish (Percidae, Centrarchidae, Peociliidae, Cyprinodontidae), but their diet can also include aquatic invertebrates and insects. Although not particularly fast swimmers, they are effective aquatic hunters, relying on their quick necks and sharp bills to catch prey. They target slower-moving species of fish and stalk them underwater, finally striking out with their long neck and spearing the prey with the beak. They then bring the prey above water and manipulate it in order to swallow the fish head first.
Animal Foods: fish; insects; aquatic crustaceans
Primary Diet: carnivore (Piscivore )
The northernmost distribution of Anhinga anhinga leucogaster is in the United States from North Carolina to Texas. It has however been spotted as far north as Wisconsin. Its range also includes Mexico, Central America, Panama, and Cuba. The individuals found in the more northern areas of the U.S. migrate there in March and April and stay until October, then return to Mexico and more southern parts of the U.S. Anhinga anhinga anhinga is found in South America from Colombia to Ecuador, east of the Andes to Argentina, and in Trinidad and Tobago. The range is limited by cool temperatures and low amounts of sunshine.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Anhinga anhinga prefers freshwater and coastal aquatic habitats that include shrub or tree-covered islands or shores; these habitats include lakes, marshes, swamps, mangrove swamps, shallow coastal bays, and lagoons. Within such habitats, anhingas are able to stalk slow-moving prey and seek refuge from danger in the water, and perch and sun itself in the treetops.
Aquatic Biomes: lakes and ponds; rivers and streams; coastal
Other Habitat Features: riparian ; estuarine
Range lifespan
Status: wild: 16.4 (high) years.
Average lifespan
Status: wild: 143 months.
Anhingas have an average body length of 85 cm, weight of 1350 g, wingspan of 117 cm, and bill length of 81 mm. The head is small and appears to be merely an extension of its long snake-like neck. In the neck, the 8th and 9th cervical vertebrae create a hinge-like apparatus that allows the quick catching of prey. The long, sharp, serrated bill also aids it in hunting. The wings are broad, allowing it to soar, and the feet are webbed to facilitate swimming. The physical structure of the legs is, however, more suited to crawling out of water onto land and for climbing bushes and trees. The tail is long and is used for providing lift, steering, braking, and balancing. When spread in flight, the tail resembles that of a turkey. The overall body shape of anhingas resembles that of a cormorant; the hunting action of the head and neck is more similar to a heron.
Anhingas are sexually dimorphic; males have brighter colors than females. Males have greenish-black plumage overall, accentuated by silver-gray feathers on the upper back and wings that are edged with long white plumes. They also have black crests. Females are brown with a lighter brown head and neck; juveniles are a uniform brown color. Molting of all flight feathers at the same time render them flightless for a while. Unlike some aquatic birds, all of the body feathers become completely wet upon contact with the water, allowing them to dive through the water more easily. This feature, however, causes them to have little buoyancy, to lose heat quickly, and hinders flight.
Average mass: 1350 g.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes colored or patterned differently
Average mass: 1080 g.
Average basal metabolic rate: 3.2258 W.
Anhingas are monogamous and pairs may reuse nests from year to year. The male begins courtship by soaring and gliding, followed by marking a possible nest location with leafy twigs. Then he performs behavioral displays to attract the female. Once the pair is formed, the male gathers nesting material, while the female builds a platform nest, which is usually on a branch overhanging water or in open areas in the tops of trees. The female constructs the nest by weaving sticks together and padding it with live twigs and green leaves. Usually, the highly territorial males defend any threats to nesting territories with extensive displays and even fighting. If another male approaches the territory, the resident male spreads its wings and snaps its beak. If no retreat occurs, fighting will commence by pecking at each other's heads and necks. Females are less aggressive, but will defend the nest if necessary.
Mating System: monogamous
Anhingas are believed to reach sexual maturity around two years of age. Breeding occurs seasonally in North America. In sub-tropical or tropical latitudes, breeding can occur throughout the year, or be triggered by wet or dry seasons. The female lays one egg every one to three days, until she has a clutch anywhere from two to six eggs. Average clutch size is four eggs. The oval-shaped eggs are bluish-white or pale green, sometimes occurring with brown speckles.
Breeding season: Anhingas may breed seasonally or throughout the year, depending on latitude.
Average eggs per season: 4.
Range time to hatching: 25 to 30 days.
Average fledging age: 6 weeks.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
The parents share in incubating the eggs for 25 to 30 days. In Mexico, anhingas were documented as performing particular displays when males and females switch incubating duties at the nest. These displays included two parents vocalizing to one another, and the incubating bird neck-stretching toward the mate. After the birds intertwined necks and the returning bird passed nesting material to the incubating bird, the two switched places. Upon hatching, anhinga chicks are naked and helpless. They eventually grow a white down on their belly side and a dark down on their back side. At first the parents feed the chicks by dripping fluid and regurgitated material from partially digested fish down their throats. As the chicks grow older, they shove their heads down the parents' beaks to get this food material. The chicks are in the nest approximately three weeks, but if threatened, are able to drop into the water and swim away, later climbing out of the water and back into the nest. At the end of three weeks, they are able to climb out of the nest to a branch, and fledge at approximately six weeks. They stay with their parents for several more weeks before becoming independent.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Protecting: Male, Female)
