The wing span of the black stork is 185-205 cm. It resembles the white stork, but is a little smaller than its relative and has a black neck and the underside of its wings is black. An adult bird is white from its chest down to the underside of its tail, the rest of its plumage is black with a strong purple-green metallic shine and its beak and legs are red. In case of a young bird, the black colour of the plumage is replaced with dark brown and the olive green of the legs and beak range with greyish pink. Ancient Estonians believed that this timid and rarely seen inhabitant of the woods pordents death. Probably this bird with a deathly black “cloak” was also the one “generally considered a holy bird” (Helme). It is likely that the bird called “piva-lind” (the holy bird) in the Livonian language also indicated the black stork. Sadly, no one remembers the ancient Estonian names for the black stork, however, Russian linguists have discovered that, in the old Novgorod region, the word “aist” (stork) had the same meaning as the word “estonets” (an Estonian) does today to the people of that area.
The main food of the black stork includes all kinds of fish and amphibians that it prefers to catch from small forest rivers and ditches. On rarer occasions, the black stork can be seen feeding from lakes, fish ponds, shallow seawater, and meadows. Research in recent years indicates that male birds can fly distances of up to 25 km from the nest to reach good feeding grounds.
The black stork is a migratory bird. The male birds reach Estonia by the beginning of April, even before the snow and ice have melted and the female birds follow a week or two later. During the period 1987 – 1996, the earliest date of sighting was March 16th, the average arrival time was March 30, and the last autumn sightings occurred during the middle of September. The black stork travels to its wintering area, extending from the Mediterranean countries to the Equator, either alone or in a small group. After returning, the male birds start to repair their nests right away to win the approval of the soon-to-arrive female birds. Since Estonia is situated on the northern border of the black stork habitat, not all male birds find mates here. Black storks attain sexual maturity at three years of age. The oldest known black stork living in the wild reached the age of 18 and its zoo-dwelling counterpart survived till 30. After mating, the female bird lays 2-5 (6) eggs and the parents take turns brooding the eggs for approximately five weeks. After the chicks have hatched, one adult bird always stays with the nest in order to guard its offspring against predators and unfavourable climate conditions. As the young birds grow and their needs increase, both adult birds have to leave in search of food. At the beginning of August, the offspring fly out of the nest, but still return to stay the night for a week or two.
Distribution and numbers
The black stork is common from Western Europe to the Far East and the population of the species is estimated at 15,000 pairs. The number of black storks nesting in Estonia has fluctuated greatly since the middle of the 20th century. At the beginning of the 1960s, an estimated 150 pairs nested in Estonia. This was followed by a significant increase in the population—according to the bird atlas, 250 pairs nested in Estonia at the beginning of the 1980s. During the last 20 years, the number has fallen to 100-115 pairs. Serious attention must therefore be paid to the protection of the black stork, and in addition to protected nesting sites, it is necessary to preserve former nesting sites, so that the population can increase. Meanwhile, the black stork has started expanding its habitat towards the west and has begun nesting in several Western European countries like Belgium, France, Luxembourg and Italy. A similar tendency has been noted in Estonia—until 1970, no proof existed of the black stork nesting on our western islands, but now the distribution map shows that Saaremaa has become one of Estonia’s most densely populated counties. The nesting sites of the black stork are located in larger forest masses, far from human habitation. Their preferred forests include marshland forests and mixed forests, but black stork nests can also be found in moorland pine forests.
The choice of a nesting site is affected by three main criteria:
- an old tree with strong branches, fit for nest construction
- nearby suitable feeding grounds: shallow, sheltered water(course)s
- lack of disturbances
The results of the Black Stork broods in 2004, 2005 and 2006 are as follows:
|Number of occupied nests with known breeding results||43|
|Number of successful nests||14|
|Nest success (%)||32|
|Total number of fledglings||29||27||37|
|Mean number of fledglings per occupied nest||1,3||1,1||0,86|
|Mean number of fledglings per successful nest||2,7||2,6||2,64|