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 BackgroundThree populations of the Cygnus c. bewickii subspecies exist: an eastern population which winters in Japan, China and Korea; a much smaller population which winters in the Caspian Sea region; and those breeding west of the Ural mountains in northern Russia winter in Northwest Europe (Wetlands International 2006; Syroechkovski 2002). Northwest European Bewick’s Swans breed at high latitudes in Arctic Russia from the Fenno-Russian border east to the Lena Delta. Birds migrate through the Baltic Sea to winter primarily in the Netherlands and Britain, with smaller numbers regularly occurring in Germany, Denmark, Belgium, Ireland and France (Beekman et al. 1985; Rees et al. 1997a). The winter distribution of the Bewick's Swan in Northwest Europe is highly concentrated. In Britain, it has a southerly distribution with the largest flocks in eastern England, especially at the Nene and Ouse Washes. Smaller flocks occur in western England, and relatively small numbers in Wales. In Northern Ireland, the only flocks of note occur at Loughs Foyle, Neagh & Beg. In the Republic of Ireland, Tacumshin Lake, Wexford Slobs and The Cull & Killag are the key resorts, all in the southeast of the country, although numbers at these sites have undergone a period of long-term decline. In Britain and Ireland, Bewick's Swans winter on shallow freshwater lakes, marshes or slow-moving rivers, near or adjacent to extensive grasslands liable to flooding. Since the early 1970s, they have taken to foraging on agricultural land, especially on waste root crops, grain stubbles and winter cereals. This switch in diet may be attributed to changes in natural habitat quality imposed by land drainage and land claim and to more extensive planting of arable crops influencing feeding site selection by the birds. Generally, Bewick's Swans in Britain and Ireland switch from arable foods to natural grasses through the winter. Proportionately, however, arable foods remain the most important over the whole winter period. The increased use of agricultural areas in southeast England may result in some conflict with agricultural interests, particularly on re-seeded grasslands and winter cereals. Although this population is protected throughout its range, ringing recoveries show that over 7% had been illegally shot or deliberately taken by humans (Brown et al. 1992, Rees & Bowler 2002). Furthermore, X-ray analysis has shown that some 40% of birds caught for ringing have lead shot in their body tissues (Rees et al. 1997a). This shows that illegal hunting occurs along the migration route, and it is known to have occurred in the UK (Evans et al. 1973). Numbers at many wetland sites in England and Northern Ireland have been monitored by WeBS since the late 1960s. Some key sites, notably Ouse Washes and Martin Mere, are used primarily as roosts, and additional roost counts are made, usually fortnightly. An International Census - when additional non-wetland sites are visited - has been undertaken once every five years since the mid 1980s. Age assessments in the UK have been conducted annually at several key wintering sites (namely WWT Centres at Slimbridge, Ouse Washes and Martin Mere) by experienced observers between 1 December and 31 January (Rees et al. 1997b). Age assessments are now being undertaken at an expanded network of sites.
Wildfowl & Wetlands Trust
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