Saturday, 2 February 2013

Anhinga


order : Pelecaniformes      Genus & Species : Anhingidae     Family : Anhinga anhinga

The anhinga seems a curious mixture of other birds, with the head, neck and wings of a heron, and the feet and plumage of a cormorant. Nonrepellent feathers are a mixed blessing for the anhinga; they reduce its buoyancy, making it superb at fishing, but they must be dried quickly to stop it from catching a chill. They found in South America, from Uruguay and southern Brazil to Ecuador, Colombia and Panama; also north through Mexico to southeastern U.S. 

Habitat : Unlike its marine relatives, the anhinga is usually found in freshwater habitats, perching on branches next to lakes, marshes and rivers. Brackish estuaries, mangrove swamps and shallow bays also play host to the anhinga. Wherever it lives, waterside vegetation is a standard feature and provides safe nesting and roosting sites. 
Food & Hunting : Fish feature heavily, but not exclusively, in the anhinga’s diet. Across its range, it consumes various species, the majority being under 4" in length and slow moving. The anhinga also preys on aquatic amphibians, reptiles, mollusks, leeches and crustaceans. A typical hunting foray starts with a serene, splash-free dive under the water. The anhinga hunts in the shallows among aquatic vegetation. Although it often stalks its prey for a minute or more, it seldom gives chase for long and prefers to wait in ambush. It has a habit of spreading its wings when it hunts; the precise reason is unknown, but it may act as a lure, tempting fish to approach what appears to be a shady resting place. As soon as a fish comes within range, the bird strikes. A hinge mechanism between its neck vertebrae and powerful neck muscles enables the anhinga to straighten its neck with lightning speed. Its victim secured, the anhinga comes to the surface to eat its meal. 
Behavior : The daily life of the anhinga is not a hectic one. In food-rich areas, the bird doesn’t invest all its time hunting. Instead, it spends most of the day sunning and preening itself in loose groups of fewer than 10 birds, but occasionally as many as 100. Nevertheless, the anhinga is not overtolerant of its own species and squabbles often occur at shared perches. In the air, the anhinga has a graceful flight, alternating between flapping and gliding. Its long tail helps it maneuver deftly among the dense vegetation, and its broad wings enable it to soar to great heights on thermals (warm columns of rising air). The anhinga has poor insulation against the cold, confining it to mostly tropical and subtropical latitudes.Those populations that breed at the northern limits of its range, most notably those in south-central U.S., desert their nesting grounds in October and fly to warmer wintering grounds in Mexico. 
Breeding : Breeding for many anhinga populations is a seasonal affair; even in those areas where the birds can nest all year-round, there is a distinct peak.The anhinga is faithful to its partner, forming a pairbond that may last several years.The pair often reuses a nest from the previous season; when not possible, it builds a nest from sticks and leaves among the reeds, bushes or overhanging branches. The female lays a clutch of up to five pale-green eggs that are incubated by both parents for four weeks. The chicks hatch naked, but soon grow a coat of buff-colored down.The chicks develop fast and leave their parents after two months.

Bill : The daggerlike mandibles have backward-pointing serrations at the tip, enabling the bird to grip its slippery prey. 
Plumage : The anhinga does not have waterrepellent plumage, which makes it less buoyant, but gives it added mobility when hunting underwater. 
Feet : Full webbing between the four toes creates a large paddling surface for propelling itself through the water. 
Tail : The anhinga uses its long tail to steer underwater. 

Weight : 2.9–3.1 lbs.
Length : 32.5-36.5"
Wingspan : 4'
Sexual Maturity : 2 years
Breeding Season : Varies with location 

The anhinga tolerates other birds and is often found in mixed breeding colonies with egrets, ibises and cormorants.