Black tern

Chlidonias niger

Photo by Jari Peltomäki (Luonto Portti)

Common name:
black tern (en); gaivina-preta (pt); guifette noire (fr); fumarel común (es); trauerseeschwalbe (de)

Taxonomy:
Order Charadriiformes
Family Sternidae

Range:
This species breeds throughout most of Europe, western Asia and North America, as far north as Finland and the Northwest Territories of Canada and as far east as Kazakhstan and western Mongolia. They migrate south to winter along the western coast of Africa, along the coats of Central America and northern South America and along the Nile river.

Size:
These birds are 22-28 cm long and a wingspan of 56-65 cm. They weigh 50-75 g.

Habitat:
The black tern breeds in fresh or brackish water wetlands with dense vegetation and pockets of open water, such as marshes, lakes, slow-flowing rivers, ditches, swampy meadows, peat bogs or rice fields. Outside the breeding season they are mostly found in coastal habitats such as estuaries, saltmarshes and coastal lagoons, as well as marine water up to 600 km offshore, but also use some inland wetlands.

Diet:
They feed on small freshwater fishes, small molluscs, tadpoles and frogs, worms, crustaceans and insects such as damselflies, dragonflies, mayflies, grubs and various larvae. Outside the breeding season also small marine fish such as anchovies and silversides, and planktonic crustaceans.

Breeding:
Black terns breed in May-August. They nest in small colonies, each being made of dead water plants, either floating or on the ground very close to water. The female lays 2-4 light-brown eggs with large dark blotches, which are incubated by both parents for 19-23 days. The chicks leave the nest soon after hatching and are able to walk or swim in search of food, but only start flying 20-25 days after hatching. They reach sexual maturity at 2 years of age.

Conservation:
IUCN status - LC (Least Concern)
This species has a very large breeding range. Although there are no estimates of global population size, the black tern is considered widespread and relatively common. The population has undergone a decline both in Europe and North America, mainly due to habitat loss to drainage and agriculture, habitat degradation, human disturbance and reduced prey availability caused by pollution, pesticides, lake acidification and the introduction if exotic fishes. Overfishing may affect food availability in some wintering areas.