Population development of Common Tern Sterna hirundo and Arctic Tern S. paradisaea along the North Sea and Baltic Sea coasts of Germany

Suedeck, P.; Haelterlein, B.; Knief, W.; Koeppen, U.

Vogelwelt 119(3-5): 147-163

1998


ISSN/ISBN: 0042-7993
Accession: 011168306

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Abstract
In 1995, 7557 breeding pairs of Common Tern and 7329 pairs of Arctic Tern were counted along the German coasts. This is over 25 % less than in a similar survey 1939 (SCHULZ, 1947). The population development of each species is described separately for the North Sea coast of Niedersachsen/Hamburg and Schleswig-Holstein and the Baltic Sea coast of Schleswig-Holstein and Mecklenburg-Vorpommern, respectively. Both species showed similar population trends during most parts of this century with peaks in the 1920s and 1930s, 1950s and 1980s. Population lows were reached just after Second World War and in the 1960s. In recent years, the population size of Common Terns decreased whereas Arctic Tern population was stable or slightly increasing along the North Sea. Direct persecution in the first half of the century and heavy chemical pollution in the southern North Sea in the 1960s have been responsible for strong decreases. The establishment of reserves and the direct guarding of colonies together with a decrease in the levels of chemical pollutants led to recovery of tern populations. Tern habitats are subject to natural succession of vegetation cover and dynamic changes in coastal landscape. The denser the vegetation cover, the less favourable it is as tern breeding habitat; such areas are usually taken over by gulls. Predation can speed up these changes of breeding bird community. The availability of alternative nesting sites which appear as early successional stages of dunes, sandflats or saltmarshes, is of utmost importance for the conservation of tern populations. Coastal protection measures have reduced the natural formation of such areas. Limited accessibility of fish is discussed as a potential cause of the recent population decline of Common Terns. This could explain why Arctic Terns have not been equally affected because they feed to a larger extent on invertebrates.