| Black tern | |
|---|---|
_a_(4644831482).jpg) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Laridae |
| Genus: | Chlidonias |
| Species: | C. niger |
| Binomial name | |
| Chlidonias niger | |
 | |
Breeding Migration Nonbreeding | |
| Synonyms | |
Sterna nigraLinnaeus, 1758 | |
Theblack tern (Chlidonias niger) is a smalltern generally found in or near inland water that breeds inEurope,Western Asia andNorth America. In winter the birds migrate to coastal areas of Africa and South America.
The black tern wasformally described in 1758 by the Swedish naturalistCarl Linnaeus in thetenth edition of hisSystema Naturae under thebinomial nameSterna nigra.[2] Linnaeus specified thetype location as Europe but it is now restricted toUppsala in Sweden.[3] The black tern is now one of four species placed in thegenusChlidonias that was introduced in 1822 by the French naturalistConstantine Rafinesque.[4] The genus name is fromAncient Greekkhelidonios, "swallow-like", fromkhelidon, "swallow": another old English name for the black tern is "carr (i.e. lake) swallow".[5] The species name is fromLatinniger "shining black".[6] As its name suggests, it has predominantly dark plumage. In some lights it can appear blue in the breeding season, hence the old English name "blue darr".[7]
Twosubspecies are recognised. These are listed below with their breeding ranges.[4]
| Image | Subspecies | Distribution |
|---|---|---|
 | C. n. niger (Linnaeus, 1758) | inland Europe (except British Isles and north Scandinavia) to central Asia, central south Russia and northwest Mongolia |
 | C. n. surinamensis (Gmelin, JF, 1789) | inland central westNorthwest Territories and eastBritish Columbia to southJames Bay and southeastMaritime Provinces (northwest to southeast Canada) to central California,Kansas,Great Lakes andMaine (northwest, central west to northeast USA) |
Adults are 25 cm (10 in) long, with a wingspan 61 cm (24 in), and weigh 62 g (2+1⁄8 oz). They have short dark legs and a short, weak-looking black bill, measuring27 mm (1+1⁄16 in), nearly as long as the head. The bill is long, slender, and looks slightly decurved. They have a dark grey back, with a white forewing, black head, neck (occasionally suffused with grey in the adult) and belly, black or blackish-brown cap (which unites in color with the ear coverts, forming an almost complete hood), and a light brownish-grey, 'square' tail. The face is white. There is a big dark triangular patch in front of the eye, and a broadish white collar in juveniles. There are greyish-brown smudges on the ides of the white breast, a downwards extension of the plumage of the upperparts. These marks vary in size and are not conspicuous. In non-breeding plumage, most of the black, apart from the cap, is replaced by grey. The plumage of the upperparts is drab, with pale feather-edgings. The rump is brownish-grey.
TheNorth American race,C. n. surinamensis, is distinguishable from the European form in all plumages, and is considered by some to be a separate species.
In flight, the build appears slim. The wing-beats are full and dynamic, and flight is often erratic as it dives to the surface for food; similar to other tern species.
Its call has been described as a high-pitched "kik"; the sound of a large flock has been called "deafening".
Hybridisation between this species andwhite-winged tern has been recorded from Sweden[8] and the Netherlands.[9] Two juvenile birds atChew Valley Lake,England, in September 1978 and September 1981, were also believed to be hybrids; they showed mixed characters of the two species, specifically a combination of a dark mantle (a feature of white-winged black) with dark patches on the breast-side (a feature of black tern, not shown by white-winged black).[10][11]
Their breeding habitat is freshwater marshes across most ofCanada, the northernUnited States and much ofEurope and westernAsia. They usually nest either on floating material in a marsh or on the ground very close to water, laying 2–4 eggs.
InEngland the black tern was abundant inthe eastern Fens, especially inLincolnshire andCambridgeshire, until the early nineteenth century. TheWelsh naturalistThomas Pennant, describing a visit made to Lincolnshire in 1769, referred to 'vast flocks' of black terns that 'almost deafen one with their clamors'.[12] Extensive drainage of its breeding grounds wiped out the English population by about 1840. Intermittent attempts by the black tern to recolonise England have proved unsuccessful, with only a handful of English breeding records, and one in Ireland, in the second half of the twentieth century.
North American black ternsmigrate to the coasts of northernSouth America, some to the open ocean. Old World birds winter inAfrica.
Unlike the "white"Sterna terns, these birds do not dive for fish, but forage on the wing picking up items at or near the water's surface or catching insects in flight. They mainly eat insects and fish as well as amphibians.
The American race has occurred as avagrant in Britain[13][14] and in Ireland.[15][16][17]
The North American population has declined in recent times due to loss of habitat.
The black tern is one of the species to which theAgreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
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