The Black stork (Ciconia nigra) is a large elegant wading bird that is widespread but uncommon species throught its native range. Black storks are long-distance migrants traveling on average between 37 and 80 days. During their long migration, they must cross the Mediterranean at the narrowest points, and many birds travel south through the Bosphorus, as well as the Sinai and Gibraltar.
The Black stork has long red legs, a long neck, and a long, straight, pointed red beak. The plumage is black with a purplish green sheen, except for the white lower breast, belly, armpits, axillaries, and undertail coverts. The breast feathers are long and shaggy, forming a ruff that is used in some courtship displays. The black stork has brown irises and bare red skin around its eyes. The sexes are identical in appearance, except that males are larger than females on average. Molting takes place in spring, with the iridescent sheen brighter in new plumage. It walks slowly and steadily on the ground and like all storks, it flies with its neck outstretched. The juvenile resembles the adult in plumage, but the areas corresponding to the adult black feathers are browner and less glossy. The scapulars, wing, and upper tail coverts have pale tips. The legs, bill, and bare skin around the eyes are greyish-green. It could possibly be confused with the juvenile yellow-billed stork, but the latter has paler wings and mantle, a longer bill, and white under the wings.
During the summer, Black storks are found from Eastern Asia (Siberia and northern China) west to Central Europe, reaching Estonia in the north, Poland, Lower Saxony and Bavaria in Germany, the Czech Republic, Hungary, Italy, and Greece in the south, with an outlying population in the central-southwest region of the Iberian Peninsula. Black storks are migratory and spend winters in tropical Africa and Asia; certain populations are sedentary or dispersive. There is also an isolated population in Southern Africa. Black storks prefer to live in more wooded areas and breed in large marshy wetlands with interspersed coniferous or broadleaved woodlands. They are also found in hills and mountains with creeks nearby. They usually inhabit ponds, rivers, edges of lakes, estuaries, and other freshwater wetlands. Black storks prefer to stay far from areas inhabited by humans and although they occur in more agricultural areas in the Caspian lowlands, they try to avoid close contact with people.
Black storks are wary birds. They usually spend time alone or in pairs, or flocks of up to 100 birds when migrating or during winter. Black storks are active during the day. They forage for food mostly in fresh water, though they may look for food on dry land at times. They wade patiently and slowly in shallow water, often alone or in a small group if food is plentiful. They may shade the water with their wings while hunting. In India, they often forage with White storks, Woolly-necked storks, Demoiselle cranes, and Bar-headed geese. Black storks communicate using various calls. Their main call is a 'chee leee', which sounds like a loud inhalation. They make a hissing call as a warning or threat. When displaying males produce a long series of wheezy raptor-like squealing calls. The young clatter their bills when aroused. Black storks also use an up-down display for a number of interactions with other members of the species. Here a stork positions its body horizontally and quickly bobs its head up from down-facing to around 30 degrees above horizontal and back again while displaying the white segments of its plumage prominently, and this is repeated several times. The display is used as a greeting between birds, and - more vigorously - as a threat display.
Black storks are carnivores (piscivores). They mainly eat fish, including small cyprinids, pikes, roaches, eels, budds, perches, burbots, sticklebacks, and muddy loaches. Their diet may also include amphibians, small reptiles, crabs, mammals and birds, and invertebrates such as snails, mollusks, earthworms, and insects like water beetles and their larvae.
Black storks are serially monogamous and pairs are formed only for one breeding season. The time of breeding varies depending on location. In the Northern Hemisphere, they breed between April and May and lay eggs in late April. In southern Africa, breeding takes place in September-March, from April and May in Zimbabwe, Botswana, and northern South Africa, and as late as July further south. During courtship pairs perform unique aerial displays. Paired birds soar in parallel, usually over the nest territory early in the mornings or late afternoons with one bird splaying the white undertail coverts to the sides of the narrowed black tail and the pair calls to each other. Black storks construct large nests from sticks and twigs, and sometimes also large branches, at an elevation of 4-25 m (13-82 ft). They prefer to nest in forest trees with large canopies where the nest can be built far from the main trunk - generally in places far from human disturbance. In mountainous areas such as parts of Spain, South Africa, and the Carpathian Mountains they nest on cliffs, on large boulders, in caves, and under overhanging ledges. Pairs nest solitarily at least 1 km (0.6 mi) apart. The female lays 2-5 large eggs and both parents incubate them for about 32-38 days. The chicks are helpless when they hatch and remain dependent on their parents for food and protection. They fledge in 60-71 days and join the adults at their feeding grounds. However, for another 2 weeks, the young continue to return to the nest, to be fed and to roost at night. They become reproductively mature by 3-5 years of age.
Although Black storks are widespread, they are not abundant anywhere. Their numbers have declined for many years in Western Europe, and the species has been extirpated as a breeding bird from the northwestern edge of its range, including the Netherlands and Scandinavia; for example, small numbers used to breed in Denmark and Sweden, but none verified after the 1950s. The population in India which is a major wintering ground is declining. Previously regular winter visitors to the Mai Po Marshes, Black storks are now seldom seen there and appear to be in decline in China overall. Their habitat is changing rapidly in much of eastern Europe and Asia. Black storks are also hunted in some countries of southern Europe and Asia, such as Pakistan, and breeding populations may have been eliminated there.
According to the IUCN Red List, the total population size of the Black stork is around 24,000-44,000 individuals. The national population estimates include less than 10,000 breeding pairs and less than 1,000 individuals on migration in China; less than 50 individuals on migration and less than 50 wintering individuals in Taiwan; less than 10,000 breeding pairs, less than 1,000 individuals on migration and less than 50 wintering individuals in Korea and less than 10,000 breeding pairs and less than 1,000 individuals on migration in Russia. The European population consists of 9,800-13,900 pairs, which equates to 19,500-27,800 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.
