Miroslav Bobek¹, Jaroslav Simek², Frantisek Pojer³ & Lubomir Peske⁴

Six adult males and four adult females together with six young males and two young females of the Black Stork (Ciconia nigra) were fitted with satellite (PTT) and VHF transmitters in the Czech Republic in 1995-2000. All but one young were members of completely monitored families. The tracked storks (if not died or not failure of transmitters) spent the winter period in Africa, in a belt south of Sahara; only one bird wintered in southern Spain. At least part of migration of four adult birds was repeatedly monitored, in one case even in four consecutive seasons. The tracked storks used both the south-west migration route across the Gibraltar strait (6 adults, 1 young) and the south-east route across the Bosporus or Dardanelles straits (4 adults). A young stork tried to migrate across the Apennines peninsula, unfortunately it was shot to death in Calabria (it reached this area from Croatia by crossing the Adriatic Sea). Storks left their breeding grounds in broad period from mid-August till mid-September and they arrived to sub-Saharan wintergrounds from late September till early December; migration itself took from 5 to 15 weeks. Young left breeding grounds independently to their parents; nevertheless it is very probably that siblings at least in one case left breeding area together. Both members of breeding pairs left breeding grounds and migrated independently; even along the different migration routes. Migration velocity of adult birds in Europe or Asia was slower and with more several-day or several-weeks stopovers that in total were longer on the south-east route (mainly on the Balkans peninsula) than on the south-west one. Migration in Africa was quicker and when crossing Sahara, migration velocity over 400 km per day was found few times. Negative influence of adverse weather condition on migration course was confirmed in several cases (e.g., delayed crossing of the Pyrenees or few hundred kilometres of reverse migration in case of sandstorm in Sahara). The monitored storks repeatedly performed the strong winter site fidelity. Nevertheless, their migration route in particular years was not identical (e.g., crossing the Pyrenees at their northern or southern edge). Storks left their main wintergrounds from mid-February to late March and reached the breeding sites from late March till late May; migration itself took from 5 to 10 weeks. Similarly to the autumn migration, longer stopovers were recorded in Europe or in Asia. The shortest and longest flight distance between breeding area and main winterground in Africa was found to be approximately 5000 km (western Africa) and 7.000 km (Nigeria via the south-east flyway), respectively. Illegal hunting was the main threat to the tracked storks in Europe (three of them were shot in France, Italy and Spain, respectively). Lack of safe roosting sites that force the storks to roost on ground where is the increasing danger of being predated seems to be one of the main threats during migration in Africa.