Saturday, 2 February 2013

Black Skimmer

order : Charadriiformes      Genus & Species : Rynchopidae     Family : Rynchops niger

Though full of poise and elegance when hunting over the water, the black skimmer becomes embroiled in unsightly territorial squabbles when breeding in large colonies. Propelled just above the water by its broad wings, the black skimmer dips its elongated lower mandible into the water’s surface to detect fish prey. They found along both seaboards of the U.S., Mexico and Central America, across much of tropical South America, and along the coasts of Chile and Argentina. 

Habitat : The black skimmer inhabits both coastal and inland sites, although there are differences in the habitat preferences of its three subspecies.The North American race is mostly confined to coasts, but the two South American races occur on inland waterways and only gather in coastal habitats outside the breeding season. Across its various habitats, the skimmer feeds mostly on calm, open waters such as large rivers, lakes, estuaries and tidal creeks. It relies on high densities of shrimp or fish in shallow water or near the surface of deeper water. It also requires habitats that have secluded areas for breeding and roosting. 
Food & Feeding : The skimmers have a unique fishing technique, based on precise movements and tactile foraging.When searching for food, a skimmer glides in a straight line just above the water’s surface, dipping its extended lower mandible into the water so that it ploughs a liquid furrow for as much as 100 yards. If it does not catch a fish, it typically rises at the end of the skim, turns and repeats the action, retracing its own wake of gently disturbed water. Because the skimmer’s feeding method relies on touch, it can forage during the day or night. The skimmer eats mostly small-sized fish including anchovy,mullet, herring, silversides and minnows. Its prey are typically 1–5" in length, or occasionally up to 8".The bird also snatches small crustaceans such as shrimp. 
Behavior : The skimmer usually feeds alone or in pairs, but it is essentially a social bird in all seasons. At nesting time, it gathers in colonies of up to several hundred pairs, with nests spaced at least 3' apart. The largest colonies form in areas of proven breeding success, and such stable sites often harbor colonies of terns. Skimmers are thought to benefit from this, as the terns are more aggressive birds and provide a measure of protection from predatory gulls. As nesting gets underway, there is much squabbling over territorial space. Outside of breeding season, large flocks of black skimmers are a common sight. Occasionally, 1,000 or more birds can be seen sheltering on saltmarsh flats. Like many birds, the skimmer faces the wind while resting so that its feathers do not get ruffled. 
Breeding : Pairs of skimmers gather at breeding colonies at much the same time every year. The months vary by region — in the upper Amazon Basin, most nesting takes place from May to October, while birds of the same subspecies in northern Colombia breed from October to March. The black skimmer mates for life, and the parents take turns incubating a clutch of eggs. About 3–4 weeks after being laid, the eggs are broken open by the downy chicks, and parental duties turn to brooding and bringing food. The chicks leave the nest after a week. After a further three weeks, they have grown their flight feathers and possess the characteristic bill shape of their parents. 

Bill : Both the upper and lower mandible are compressed like blades. Only the upper mandible, which is twothirds the length of the lower one, is hinged, enabling the bird to lift it above the surface of the water. 
Eyes : By day, the pupils contract to vertical slits to protect the retinas from the glare of sandy beaches and glittering water.This feature is unique to the genus Rynchops: all other birds have round pupils. 
Wings : Along with its streamlined build, the skimmer also has narrow but very long wings with a span of up to 2.5 times its bodylength. 
Legs & Feet : The bright red on the bill, and on the short legs and webbed feet, stands in bold contrast to the pied plumage. 
Chicks : When a chick hatches, the two bill mandibles are equal in length, but grow at different rates over the next few weeks. By the time the bird fledges, the lower mandible is 0.5" longer. 

Weight : Male 10–13 oz.; female 8–10.5 oz. 
Length : 16-20"
Wingspan : 42-50"
Sexual Maturity : 1-3 years
Breeding Season : Varies with location 

The black skimmer is also called the seadog because of its barklike calls, which are longer and harsher under stress.

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