Anhinga anhinga leucogaster
also known as Water Turkey or snakebird
The anhinga is a water-dwelling bird that – unlike most aquatic birds – does not have oil glands to waterproof its feathers. This means that when it is in the water its feathers get thoroughly soaked and must be dried. The anhinga does this by perching in the sunshine with its wings spread, a pose which is its most identifiable mannerism. The lack of oil glands restricts where the anhinga lives and what it can find to eat.
The anhinga is found globally in most warm climates. In English-speaking countries it is called a “darter” in reference to its quick movements. Abundant in the Americas, its native range is from the Carolinas and Texas in the United States, as far south as northern Argentina in South America, and in Mexico and various Caribbean locations. The main breeding population in the United States is found in the state of Florida, with scattered nesting sites in coastal areas of Texas and Louisiana. It also breeds along the Mississippi River in Missouri and Kentucky, where it is classed as an 'endangered' species.
Adult anhinga weigh approximately 3 pounds each with a wingspread of 4 feet and a height of 32 to 36 inches. The head is small, no broader than the long, thin neck. The bill is very long, slim and pointed. An anhinga has low buoyancy due to its feathers absorbing water and therefore swims with just its neck and head above the surface, jerking its curved neck much like a snake.
If it can launch itself in a gliding flight from a tree, an anhinga sometimes soars for an extended period, like a hawk. It has a wide, fan-shaped tail which, extended in flight, gives the anhinga the overhead flight silhouette of the native American turkey. Early Florida settlers in the Everglades sometimes mistook the anhinga for a turkey, hence the name “water turkey”. Being a fish eater, however, the anhinga is unpalatable for human consumption.
The chicks, in clutches averaging four, are born naked and helpless. By the time they are fledglings at the age of six weeks both sexes are a uniform brown color. Being dimorphic, the adult male is more brightly colored than the female. Both have dark bodies with white plumes and edgings on the wing coverts. The female is brown with a lighter buff-colored head and neck. The male has rich, greenish-black plumage and a black crest.
The long neck has a hinge-like apparatus in the 8th and 9th cervical vertebrae which accounts for the distinctive movement of the head and which allows the quick catching of prey. The bill is long, sharp, and serrated. The anhinga hunts its food underwater, feeding primarily on fish but also stalking aquatic invertebrates and insects. Crayfish, leeches, tadpoles, young alligators and water snakes are all included in the anhinga diet . The pointed beak is used to spear the prey underwater. The bird rises to the surface and jerks the prey off its bill, then manipulates it in order to swallow it head first. Sometimes the prey is so impaled on the length of the bill that the bird must swim to shore and pry the fish off by rubbing it against a rock.
Although a member of the Pelican order (Pelecaniformes), the anhinga has no apparent pouch in its lower jaw to accommodate its food. Instead, it has a very extensible skin between its lower jawbones. When drying its feathers, it often opens its beak. If positioned against the setting sun at this time, the pouch appears as a glowing red triangular-shaped balloon.
Anhinga are monogamous and a pair may reuse the same nest from year to year. They also take over nests from herons and egrets. Often small numbers of anhinga will nest with herons, cormorants, ibises, and storks. They share the same habitat - freshwater or brackish lakes and lagoons, swamps and sloughs, sluggish streams and slow canals. The anhinga co-exists with herons and egrets as it is a much slower swimmer than these and targets the slower-moving fish. Strongly territorial, it does not breed in colonies and is more apt to be found with groups of other water feeders than with its fellow anhinga. For purposes of field identification, cormorants have hooked bills and shorter tails and necks than do anhinga.
The nest is located anywhere from five to 20 feet above ground, being a platform nest on the branch of a tree. The breeding pair share nest-building with the male gathering the material and the female weaving sticks together, then padding them with twigs and green leaves. Copulation takes place on the nest with the male keeping his balance by holding onto a stick or the female’s bill with his bill.
The female lays between two and six eggs, oval-shaped and bluish-white or pale green in color. The parents share the 25- to 30-day chore of incubating the eggs, sometimes with ritualized displays as they switch incubation duties at the nest. This includes vocalizing, neck-stretching and -intertwining, and the passing of additional nesting material to the incubating bird.
Although it vocalizes on or near the nest and sometimes when perching or flying, the anhinga is normally a quiet bird. It has no significant song pattern and communicates mainly with a series of clicks, rattles, croaks and grunts. It molts all of its flight feathers at once and is unable to fly; during this period it is silent.
Anhinga are restricted to tropical and sub-tropical zones because of the lack of oil glands. Not having an insulating layer of body feathers as cormorants do, it loses heat quickly in the water and must spend compensating periods of time in the sunshine to maintain its body temperature. On dark, cloudy days it will stay out of the water. It is also limited by temperature due to its low metabolic rate.
Sources:
www.animaldiversity.ummz.umich.edu/site/accounts/information/Anhinga_anhinga.html
www.geocities.com/Heartland/5960/anhinga.html
www.miamisci.org/ecolinks/everglades/anhingainfo.html
www.usda.gov/servlet/SingleRpt/search_topic.html