Body length: 22 – 28 cm. Width of the wings: 56 – 65 cm. Weight: 50-75 g. Life expectancy: 17 years.
They have short dark legs and a short, weak-looking black bill, measuring 27 mm, 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.
Distribution and Habitat
Holarctic species inhabiting Europe and Asia from France and southern Spain to the lake of Baikal and North America – between 60 ° and 40 ° С. Migrating species, winter in Africa. Spring migration is in April, and autumn – in September. The Black Тern migrates until late in May, with intensive transitions still in the middle of the month. It is then found in many lakes along the Black Sea coast, but this cannot be considered as nesting. During migration, it is found in the waterfalls all over the country, with the flocks sometimes counting hundreds of birds.
It inhabits freshwater basins (marshes, lakes, fishponds), densely overgrown with floating aquatic vegetation.
In Bulgaria the Black Тern is a nesting and passing species. There are isolated nesting sites along the Danube River and in the Danube Plain. Ponds have some potential for nesting in the interior. During the breeding season it is registered along the Black Sea coast, the Thracian lowland and the Sofia field.
It feeds on insects, crustaceans, small fish and amphibians.
The Black Тern hatches in colonies, rarely single. The nest is located on the leaves of floating vegetation, rarely in tuft of reed. Laying eggs (usually 3 eggs) is at the end of May – until mid-June. Both parents incubate for about 21 days. Small ones appear most often by the end of June. Fugitives from the nest. They start flying after 21-25 days. Sexual maturity occurs not earlier than the second year.
In Bulgaria: critically endangered. Protected species under the Biological Diversity Act.