[order] Charadriiformes | [family] Sternidae | [latin] Chlidonias niger | [UK] Black Tern | [FR] Guifette noire | [DE] Trauerseeschwalbe | [ES] Gaviotín Negro | [IT] Mignattino | [NL] Zwarte Stern

Zwarte Stern determination

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A small, graceful, black and silver bird, the Black Tern has relatively broad wings and a short tail that is only slightly forked. In breeding plumage, it has a black body and head, silvery gray wings and a white vent. The legs and bill are also black. In non-breeding plumage, the Black Tern has a white belly and breast. The black on its head recedes, leaving dark sideburns, and is replaced with a white face. The legs are orange. Juveniles appear similar to adults in non-breeding plumage, but the gray mantle is mottled.
Black Terns swoop to pluck food from the water's surface; they rarely plunge-dive under the water. They will also forage in flight, snatching flying insects out of the air. Highly social, they often forage in flocks.

For nesting, it requires habitat with extensive, cover-providing, vegetation as well as open water. During migration, it uses large lakes and coastlines. In winter, it can be found along productive marine coastlines, lagoons and estuaries

This tern is breeding in North America and Eurasia, from the Iberian Peninsula to Central Asia. Birds of Europe winter mainly along the Atlantic coasts of Africa, from Senegal to South Africa. The population of the European Union is estimated at 3000-4000 breeding pairs, which represents only 5% of the total European population. Wetland reclamation, canalisation of rivers, extension of pisciculture, water pollution and disturbance of the breeding colonies are the major reasons for the constant decline which this species is undergoing since the end of last century.
Chlidonias niger is a widespread but patchily distributed summer visitor to much of Europe, which accounts for less than half of its global breeding range. Its European breeding population is relatively large (>83,000 pairs), but underwent a moderate decline between 1970-1990. The species declined across much of Europe (particularly the east) during 1990-2000, but the trend in its Russian stronghold was unknown. Nevertheless, its population has clearly not yet recovered to the level that preceded its decline.
Numbers have decreased since the 1960s due, in part to the destruction or degradation of much of their breeding and migration stopover habitat. Other potential impacts on the population are increased fertilizer runoff causing chemical contamination in wetlands, and overfishing in winter habitat. It is federally designated as a category 2 candidate for listing under the endangered species act, and is included on the Washington Gap Analysis list of birds at-risk.

In the breeding season, insects are the primary food source, although small fish and other aquatic creatures are also eaten. During migration and in winter, small fish make up the bulk of the diet.

This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km˛. It has a large global population estimated to be 450,000-1,300,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]

Breeding in scattered colonies, often associated with Forster's Terns, Black Terns nest low in marshes, on floating vegetation mats, muskrat houses, or on the ground near water. Both parents help build a nest which ranges from a substantial mound of vegetation to a simple depression with a little bit of vegetation added. When mixed with Forster's Terns, the Black Tern nests tend to be lower, closer to the water. In fact, the eggs of Black Terns are adapted to get wet (but not for extended periods of time), and are often moist. Both parents incubate the 2-4 eggs for about three weeks. After 2-3 days they may leave the nest, but stay close by. In approximately three weeks the young are ready to fly, but they may be fed by their parents for up to 2 more weeks. Typically only one brood is raised each year.

North American birds migrate to both Pacific and Atlantic coasts, wintering from Mexico (rarely) and Panama S to Peru, and from the Gulf Coast to N south America; accidental in Chile and Argentina. Many non-breeding birds, failed breeders or early migrants reach the coast by mid-summer; fairly common (formerly abundant) migrant off both coasts of Costa Rica; 1 st-year summer along Pacific coast. Arrives back on breeding grounds in Apr. Palearctic birds often disperses N after breeding, with sometimes very large concentrations e.g. in S North Sea; migrates in huge numbers through Mediterranean; and also across N Africa (even over deserts), to main wintering grounds on tropical W African coasts from Mauritania to Namibia, some reaching South Africa; some winter in Nile Valley. Adults begin southbound migration by Aug, juveniles about a month later. Occasional birds linger over winter on Black and Caspian Seas.