Rok co rok opouštějí milióny tažných ptáků svá hnízdiště a odlétají na jih. Ptačí tah je jedním z nejzajímavějších přírodních jevů; přestože ho ale vědci zkoumají více než sto let, stále o něm víme překvapivě málo. Teprve v poslední době nám moderní technika umožňuje sledovat ho téměř v přímém přenosu.
Miroslav Bobek (1), Jaroslav Šimek (2), František Pojer (3), Lubomír Peške (4)
(1) Czech Radio, Vinohradska 12, 120 99 Prague 2, Czech
Rep.; (2) Faculty of Biological Sciences, University of South Bohemia,
Branisovska 31, 370 05 České Budejovice, Czech Rep.; (3) Agency for Nature
Conservation and Landscape Protection of the Czech Republic, Kalisnicka
4-6, 130 23 Prague 3, Czech. Rep.; (4) Slezska 43, 120 00 Prague 2, Czech
Six males and four females of the Black Stork Ciconia nigra from the Czech Republic were fitted with satellite (PTT) and VHF transmitters in 1995-1999. Six birds used the south-west migratory route via Gibraltar. They wintered in southwest Spain, eastern Senegal, central part of Mali, western Mali and southern Mauritania, respectively. Other four storks used the south-east flyway via Israel. Their wintergrounds were in northern Ethiopia, eastern part of Central African Republic (twice) and north-eastern Nigeria, respectively. All of the storks bred in the same region in Central Bohemia, Czech Republic. Three of the storks were repeatedly monitored (female Kristyna even four times) and all of them showed strong winter-site fidelity (Spain, Senegal and Ethiopia). Storks arrived to sub-Saharian Africa from late September till early December, arrival was variable also for repeatedly monitored storks. "Buffer" zone in western and central Africa just under the Sahara was found. In this zone storks aggregate into more numerous groups. Some storks stay for the whole winter in such areas (probably mainly in western Africa). Other storks use this zone for resting and energy refueling before other migration to main wintergrounds. In the main winterground we did not find any marked movements of the birds; storks wintered individually or in small groups there and only short local movements were registered. Different wintering conditions and threats were identified by expeditions in five separate wintergrounds. Storks left their main wintergrounds from mid-February till late March. Short-distance and one long-distance (960 km) movements were found before right back migration. The Black Stork is one of the most threatened European bird species; therefore it should be appropriate to ensure effective protection of sites and habitats with higher stork aggregation.