Bewick's Swan
Tundra Swan
Cygnus columbianus Ord, 1815
Cygnus bewickii: Peshev, Boev, 1962: 328; Koenigstedt, Robel, 1979: 335.
Order Anseriformes
Family Anatidae
Conservation status: in Bulgaria: Critically endangered CR=[B+D], BDA-III; International: BeC-II, BoC-II, ECS-Spec 3W, BD-I.
General distribution. A polytypical species. It breeds in the tundra of Northern America, Northeastern Europe and Siberia. It winters in the shore lowlands of Northern Europe and Eastern Asia in the south to Taiwan. A small population of an unknown origin winters along the southern shore of the Caspian Sea in Iran. During migrations it is rarely found in Mongolia and the internal territory of Northern China.
Distribution and abundance in Bulgaria. A rarely wintering species, represented in Bulgaria by the subspecies Cygnus columbianus bewickii Yarrell, 1830. It was found for the first time near Durankulak Lake [1]. In the period until 1985 it was reported only near Atanasovsko Ezero lake [3]. After 1989 it regularly winters in small numbers mainly along the Black Sea coast, less frequently near water basins in Northern and Southern Bulgaria. Major wintering places are the wet agricultural terrains around Mandrensko Lake, near the mouth of the river Fakiyska, where its highest numbers in Bulgaria were registered: 84 individuals on 15 February 1997 [4]. For the region of the Burgas lakes it shows a tendency for an increase of the wintering population. In small numbers (from 2 to 8 individuals) it has been registered once also in the wetlands of Southern Bulgaria [5].
Habitats. Permanent internal and shore basins with different saltiness, sea shallows, bays and straits, intertidal marshes, marshy lowlands, arable land, pastures, seasonally flooded fields, meadows.
Biology. Young birds migrate together with the adults; the family is preserved until the end of the winter. It feeds mainly on underwater parts of plants, rarely on seeds; animal food is accidentally found together with the plants. In Bulgaria it is mainly registered in fields with winter wheats, very often together with the Whooper Swan, less frequently with the Mute Swan.
Similar species. The Whooper Swan (Cygnus cygnus).
Negative factors. Loss and degradation of habitats, persecution by man, pollution of the soils, spills of oil products.
Conservation measures taken. Protected according to the Biological Diversity Act. The lakes Durankulak, Shabla, Pomoriysko, Atanasovsko, Vaya and the Poda locality with Foros Bay are declared Ramsar sites, monitoring is carried out and management plans are implemented (not for Pomoriysko Lake, for which a management plan is being currently developed).
Conservation measures needed. Placing under protection the region around Mandrensko Lake, to the south of the village of Dimchevo (Burgas region) to the mouth of the Fakiyska River, introduction of compensations for owners of lands; declaring Mandrensko Lake a Ramsar site and working out a plan for its management.
References. 1. Konigstedt, Robel, 1979; 2. Nankinov et al., 1997; 3. Robel, Willems, 1984; 4. Dimitrov et al., 2005; 5. Michev, Profirov, 2003; 6. Kostadinova, Dereliev, 2001; 7. Michev et al., 2004.
Authors: Milko Dimitrov, Lyubomir Profirov
