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Titre :	Population dynamics of breeding birds in western Schleswig-Holstein: A review of changes in the period 1945 - 1995
Auteurs :	Guenther Busche, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (120(4) 1999)
Article en page(s) :	193-210
Résumé :	The study area is situated in the county of Dithmarschen, Schleswig-Holstein, Germany and covers 1405 km2 (Fig. 1, Tab. 1, 2). In the period 1993-95, 140 bird species bred regularly in the study area. Since 1945 a further 26 species have been recorded breeding irregularly in the area. 29 % of the irregular breeding species occur in Schleswig-Holstein on the edge of their respective breeding ranges. 30 % of the regular breeding species are long-distance migrants, 39 % middle- and short-distance migrants and 31 % are sedentary (Tab. 3). Fig. 2 presents the numbers and relative dominance of regular breeding species and their population sizes. Additional information on the 140 breeding species, number of species and breeding populations is presented in Tables 3 to 5. The dominant species in different regions are given in Table 6. In the period from 1950 onwards, 106 species are known to have bred each year in the study area. The species turnover rate is 54.4 (see formula in 3.1). Approximately 240,000 pairs of birds bred in the county of Dithmarschen in the period around 1995. The total density of the breeding bird population (excluding non-breeding individuals) is estimated at 171 pairs/km2. The dominant species (> 5 %) are Blackbird, House Sparrow, Chaffinch and Skylark. - The populations of 57 % of the regular breeding species have changed in the period 1961-95. 55 species (39 %) increased and 26 (19 %) decreased in the period (Fig. 3, Tab. 3, Appendix 1). Three species (2 %) became extinct (Black Grouse, Great Grey Shrike, Barred Warbler). The increases are clearly due to increases in the woodland bird populations (Fig. 4) due to the drainage of bogs (afforestation) and mainly in towns and villages. Most species undergoing population declines are ground-nesting birds. The pure agricultural areas have generally become less attractive for breeding birds. The number of individuals has increased slightly or at least has not decreased since 1960 (Tab. 5). The number of species recorded in the study area is 123 % of the value expected from the species-area relationship for central Europe (see 4.6.1.), i.e. it is larger than in comparable regions (3.5.). The reason is that for a number of species the border of their breeding ranges lies in Dithmarschen (oceanic and continental species). The changes in the number of species recorded in Schleswig-Holstein on the whole since 1950 are similar to those recorded in Dithmarschen (see turnover rate in Tab. 8). However, the recent dynamics of 124 populations in the study area are very different from the general changes recorded in central Europe. 33 % (in Schleswig-Holstein) to 46 % (in Dithmarschen) of the species show a population development different from that elsewhere.

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