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Waterbird Populations and Pressures in the Baltic Sea

image of Waterbird Populations and Pressures in the Baltic Sea

This report outlines the results of the internationally coordinated census of wintering waterbirds in the Baltic Sea 2007-2009 undertaken under the SOWBAS project (Status of wintering Waterbird populations in the Baltic Sea). The estimated total number of wintering waterbirds was 4.41 million compared to 7.44 million during the last co-ordinated census 1992-1993. Despite the general declines stable or increasing populations of herbivorous species were recorded. While benthic carnivores with a coastal distribution have either shown moderate declines, stable or increasing populations seaducks with an offshore distribution have declined seriously. Based on analyses of trends in wintering waterbirds and pressures indicators are suggested as performance indicators in relation to the international and national actions taken to reduce the anthropogenic pressures in the Baltic Sea.

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Distribution and Numbers of Waterbirds

The north-west European winter population of Red-throated Divers is estimated at 150,000-450,000 birds, while the population of Black-throated Divers is estimated at 250,000-500,000 birds (Delany & Scott 2006). The results of the present study indicate a massive decline from 56,500 birds in the Baltic Sea during 1988–1993 to 8,575 in 2007–2009, equivalent of 84.1%. As the estimated sizes of the total populations of both species of divers have been completely revised since the 1994 status report it is not possible to assess whether the decline in the Baltic winter population is a reflection a large-scale or just regional population declines. Assuming that the estimates in Delany & Scott (2006) are correct the current status indicates that between 0.9% and 2.1% of the north-west European winter populations of both species winter in the Baltic Sea. The range of the proportion of birds wintering in the Baltic Sea is caused by uncertainties regarding the sizes of recruiting populations in Russia (Delany & Scott 2006).

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