Saving wetlands for wildlife & people
Saving wetlands for wildlife & people
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Background
There are five populations of Whooper Swan: the Iceland population breeds in Iceland and winters in Iceland, the United Kingdom and Ireland; the Northwest European population breeds in Scandinavia and north European Russia and winters in northwest and central Mainland Europe; the Black Sea and east Mediterranean population breeds in northern Europe and western Siberia and winters in the Black Sea and east Mediterranean; the Caspian and central Asia population breeds in west and central Siberia and winters in the Caspian and central Asia; and the east Asia population breeds in central and east Siberia to northeast China and winters in east Asia (Wetlands International 2006). Iceland Whooper Swans breed throughout Iceland (Garðarsson & Skarphedinsson 1984). Large flocks of non-breeders and failed breeders gather on marine and brackish waters in Iceland during late summer. Most birds leave Iceland for Britain and Ireland from mid October to mid November. Sites in northern Britain and Ireland act as major landfalls, e.g. Shetland, Orkney and, especially, Loughs Swilly and Foyle in Northern Ireland (Robinson et al. 2004). Most Iceland Whooper Swans spend the winter in Britain and Ireland, although a small proportion, of up to 1,300 individuals, remain in Iceland and this number may be related to weather conditions and food supply in Iceland at this time (Garðarsson & Skaphedinsson 1984, Cranswick et al. 2002). There is evidence, however, of some interchanges between the Iceland and Northwest European populations. Ring sightings of British ringed birds in Norway, Denmark and the Netherlands suggest that up to 600 birds from the Iceland population may winter in mainland Europe while a small number of Finnish ringed birds have been sighted in Britain giving rise to the suggestion that around 200 birds from the Northwest Europe population visit Britain (Garðarsson 1991, Cranswick et al. 1997, Laubek et al. 1998). Even historically, most of the Whooper Swans that visited Britain and Ireland wintered in Ireland and Scotland. Numbers in Ireland are thought to have increased since 1900, but have remained relatively stable since the mid 1950s. In the early 1960s, East central Scotland held the largest concentrations of Whooper Swans in Britain but numbers there have since declined; numbers in the Outer Hebrides also fell over the same period. However, there has been a large increase in the numbers using Martin Mere in Northwest England and the Ouse Washes in Southeast England since the 1980s with over 2,000 recorded at these sites during the most recent census in January 2005. High numbers also occur at the Foyle/Swilly complex, Loughs Neagh & Beg and Upper Lough Erne, all in north Ireland. During the early part of the 20th century, Whooper Swans wintering in the UK fed mainly on aquatic vegetation during the winter months, particularly Zostera and Chara species in coastal areas and on the tubers and root stalks of Potomageton, Elodea canadensis, Glyceria, Equisetum and Rorippa palustre in freshwater lakes and marshes (Owen & Kear 1972). Agricultural land has been far more frequently used since the 1960s, partly as a result of agricultural intensification in the wintering areas. Feeding on potato fields was first reported in the 1940s, since when flocks have been recorded on cereal and potato stubbles, winter cereals and occasionally oil seed rape (Anderson 1944, Kear 1963, Chisholm & Spray 2002). Numbers counted at arable sites during the censuses in Britain and Ireland have not exceeded 15% of the Iceland Whooper Swan population (Cranswick et al. 2002) and very few birds were found on growing crops (3% in the Republic of Ireland and 9% in Britain) during the January 2005 census. Instead, the majority of birds recorded on arable land in January 2005 were using waste stubble and harvested potato fields (Worden et al. in prep). Although the population is protected throughout its range, ringing recoveries showed that 13% had been illegally shot or deliberately taken by humans (Rees et al. 2002). X-ray analysis of birds caught in Scotland showed that 10% had lead shot in their body tissues (Rees et al. 1997). The habitat switch of Whooper Swans on to cropped land (arable and agriculturally-improved pasture), together with an increase in the numbers of birds wintering in the UK, has resulted in some conflict with agricultural interests, particularly for re-seeded grasslands, winter cereals, root crops and oil seed rape. Numbers at many major wetland sites in Britain and Ireland have been monitored by WeBS and I-WeBS since the late 1960s. Some sites are used primarily as roosts and additional roost counts are made, usually fortnightly, at the Ouse Washes in particular. Since many sites which are used by Whooper Swans are not covered by WeBS or I-WeBS, a species-specific survey remains the most reliable means of achieving the required coverage to assess population size and trends. International censuses have been undertaken since 1986 and now occur once every five years in mid January. Age assessments in the UK have been conducted annually at several key wintering sites (namely WWT Centres at Slimbridge, Welney (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.
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