Unlike the closely related white stork, the black stork is a shy and wary species. It is seen singly or in pairs, usually in marshy areas, rivers or inland waters. It feeds on amphibians, small fish and insects, generally wading slowly in shallow water stalking its prey. Breeding pairs usually build nests in large forest trees—most commonly deciduous but also coniferous—which can be seen from long distances, as well as on large boulders, or under overhanging ledges in mountainous areas. The female lays two to five greyish-white eggs, which become soiled over time in the nest. Incubation takes 32 to 38 days, with both sexes sharing duties, and fledging takes 60 to 71 days.
During the summer, the black stork is 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 (Extremadura and surrounding provinces of Spain, plus Portugal). It is migratory, wintering in tropical Africa and Asia, although certain populations of black storks are sedentary or dispersive. An isolated population exists in Southern Africa, where the species is more numerous in the east, in eastern South Africa and Mozambique, and is also found in Zimbabwe, Eswatini, Botswana and less commonly Namibia.
The black stork prefers more wooded areas than the better-known white stork, and breeds in large marshy wetlands with interspersed coniferous or broadleaved woodlands, but also inhabits hills and mountains with sufficient networks of creeks. It usually inhabits ponds, rivers, edges of lakes, estuaries and other freshwater wetlands. The black stork does inhabit more agricultural areas in the Caspian lowlands, but even here it avoids close contact with people. Its wintering habitat in India comprises reservoirs or rivers with nearby scrub or forest, which provide trees that black storks can roost in at night.[26] In southern Africa it is found in shallow water in rivers or lakes, or swamps, but is occasionally encountered on dry land.
Migration takes place from early August to October, with a major exodus in September. Some of the Iberian populations, and also those in southern Africa, are essentially non-migratory, though they may wander freely in the non-breeding areas. A broad-winged soaring bird, the black stork is assisted by thermals of hot air for long-distance flight, although is less dependent on them than is the white stork. Since thermals only form over land, the black stork, together with large raptors,[36] must cross the Mediterranean at the narrowest points, and many black storks travel south through the Bosphorus, as well as the Sinai and Gibraltar. The trip is around 5,667 km (3,521 mi) via the western route and 7,000 km (4,300 mi) via the eastern route, with satellite tracking yielding an average travel time of 37 and 80 days respectively.
The western route goes over the Rock of Gibraltar or over the Bay of Gibraltar, generally on a southwesterly track that takes them to the central part of the strait, from where they reach Morocco. Many birds fly around the Sahara next to the coast. About 10% of the western storks choose the passage between Sicily (Italy) and Cap Bon (Tunisia), crossing the Strait of Sicily.
Spain contains several important areas—Monfragüe National Park, Sierra de Gredos Regional Park, National Hunting Reserve in Cíjara, Natural Park of the Sierra Hornachuelos and Doñana National Park—where black storks stop over on the western migration route. Pesticide use has threatened birdlife in nearby Doñana. Further south, Lake Faguibine in Mali is another stopover point but it has been affected by drought in recent years.
